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When to test for HIV during and after completion of PEP

I get this question a lot.

First of all, data on this is lacking and very hard to come by.

There are many theories that hypothesize that PEP reduces viral replication and delays sero-conversion and therefore make HIV testing less accurate. These theories have neither been proven nor debunked.

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Furthermore, there is very limited data on the use of P24 antigen tests (including Combo/Duo tests) and viral load testing for diagnostic purposes in patient who have or undergoing PEP. In fact, studies on monkeys (and more limited studies on humans) have shown positive viral load tests in individuals who were subsequently found not to be infected. This could represent an aborted infection (which is what PEP is supposed to and designed to do) rather than a true false positive. This illustrates one of the limitations of using viral load tests to diagnose people currently on or have completed PEP.

Official Guidelines

The US CDC Guidelines on Antiretroviral Postexposure Prophylaxis After Sexual, Injection-Drug Use, or Other Nonoccupational Exposure to HIV in the United States recommends that patients should be tested for the presence of HIV antibodies at baseline, 4 – 6 weeks, 3 months and 6 months post exposure.

The Joint WHO/ILO guidelines on post-exposure prophylaxis (PEP) to prevent HIV infection recommends HIV testing at baseline, immediately after completing PEP (i.e. 4 to 6 weeks post exposure) and again ‘3 – 6 months post exposure’.

The 2 guidelines are rather similar although the US CDC seems to be more firm on the requirement of a test at 6 months compared to the WHO guidelines.

Very recently, the New York State Department of Health AIDS Institute’s adult HIV guidelines committee undertook a comprehensive re-evaluation of its HIV occupational PEP guidelines and issued some changes which included shortening of the time of HIV testing after exposure to 3 months if modern, blood based, standard HIV testing is performed. This is certainly promising however it refers to occupational HIV exposure only and the same data and recommendation may not be extended to non-occupational exposure.

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 In short, most official guidelines still recommend testing at 6 months for patients who have undergone PEP.

Sometimes testing at 3 months post exposure is good enough but this really depends on what kind of test is done.

My own experience is the test done at 4 weeks exposure (or immediately upon completion of the PEP medications) is very indicative. I will still recommend a retest at 3 months although I have yet to see the test at 4 weeks get it wrong.

At the end of the day, the best person to advise you is still the doctor who prescribed you the PEP. He/She will be most familiar with the sensitivity of local tests available and the local guidelines.

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About Dr. Tan
Dr. Tan graduated from the National University of Singapore in 2001. His residency was in the two largest public hospitals in Singapore; Tan Tock Seng Hospital and Singapore General Hospital.

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  1. Doctors hello:
    I previously dangerous sex after taking PEP28 days
    Taking has successfully completed all the PEP
    Have a decisive test this long? Example: is elisa combo or the pcr …
    I was in Taiwan, my doctor followed six months of the antibody test is very conservative
    Ask you!
    How often should I have a decisive test, I think I bring you trouble, thank you!
    (Sorry my English is very poor hope you will forgive me
    I’m sorry I should leave a message on this page!)

    • Hello to Taiwan from Singapore. I love Taiwan. Great place for a holiday. Your doctor is absolutely right. Most medical guidelines still recommend testing up to 6 months for patients who have taken PEP. Some authorities have brought this down to 3 months. From my personal experience, the HIV antibody test done at 4 to 6 weeks post exposure (i.e. upon completion of PEP to 2 weeks post PEP) is already very very accurate. Both the PCR and Combo tests have not been adequately studied in post PEP patients so it makes it very difficult for me to comment on them. Please post any follow up questions on http://www.askdrtan.com

      • Thank you for your replies carefully, I wish you have a nice day ^ _ ^

  2. Hello Doctor:
    If I have a PCR test three months after PEP completed
    You would think that a high degree of accuracy?
    PEP affect the virus after 3 months after PEP
    I think that would be incredible … do you think?
    Disturb you again sorry..Thank you very much!

  3. Wow, this Dr. really keeps apace the current research!

  4. Hi from Brazil. You have the most up to date data on testing when it comes to PEP. There are a lot of confusing data and this is what suits most to what I need now. I´ve have just taken PEP and took a Rapid test immediatly after finishing PEP (negative, thank god) Ive read some saying that I should wait a month after finishing PEP to get tested but now after reading your article Im a lot calmer. I also took an ELisa test as a confirmation at the same day of the rapid test, but my health care told me I should not worry because the rapid test is as efficient as the latter. After all I confirmed that all the instructions they gave me was just right.Thank you so much!

  5. DR Tan
    Hy am from South Africa. I was expose to an hiv + woman on the first weekend of september. The nurse at the clinic offered me a pep treatment (Sonke-Lamivudine 150mg and Zidovudine 300mg ) 68 hour . I tested hiv- using rapid on the 2 week after my pep treatment, 6 weeks after exposure. What are the odds of the results changing to + on the next 6 week, 3 and 6 months after exposure? How conclusive or accurate is my two week test after finishing pep treatment?

    Thank u

    • Extremely accurate. I personally have never seen a test at 6 weeks (2 weeks post PEP) get it wrong.

      • As nice as being told that everything is gonna be alright, these assumptions are probably not accurate PEP reduces the level of Virus after 2 weeks it is unlikely that any test will show antibodies. please see table 1 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC109656/

        • Thank you for sharing the information. First of all I would like to point out that these studies are on SIV (Simian Immunodeficiency Virus) and not HIV. Although you are absolutely right that there can some parallels that can be drawn, we must be careful not to make exact comparisons. I looked at the table you highlighted. From what I can gather, the control group were all infected and antibodies detected at 4 weeks for all. The 24 hours group were all protected with no antibodies at 4 weeks, 12 weeks, or 16 weeks. There were antibodies detected at 32 weeks 1/2 but all non-viraemic ? false positive. For the 48 hours group, there were no antibodies detected at 4 weeks but all at 12 weeks which is in keeping with current guidelines for human testing i.e test at 4 weeks and again at 12 weeks. This is similar for the 72 hours group. I am looking at the groups on the 28 days regime. That is why although we tell patients that the post PEP test at 4 weeks is very accurate, we always insist on a retest at 12 weeks. If there was no chance that the 12 weeks test will turn positive, we would not recommend our patients to test at 12 weeks. That said, human studies show that statistically, the 4 weeks test is already very accurate. Thank you for sharing. I look forward to having more exchange of ideas with you.

  6. Hi,

    I was tested at four weeks post-PEP with a 3rd generation rapid antibody test, which was negative. How confident can I be this is conclusive?



  7. Greetings Doctor,

    My source was HIV negative on 33 day of post exposure still I chosed to take PEP which I started within 10 hours I completed my course of 30 days and after 32nd day post exposure I got tested on 3rd generation antibody test that is Rapid Immunochromatographic test from internationallay accredated laboratory and it cam both HIV one and HIV two non reactive how confident should I be.

    Warm Regards

  8. Actually at the time of exposure I was not aware of the status of my source and then I got scared I started with PEP for 30 days I was on duovir. Previously also I tested PCR DNA on 10th day and also P24 on same day while on PEP and then again an P24 antigen test on 7th week post exposure and then again tested on 5th week with third generation antibody test all done from an Internationally accedated laboratory how confident should I be now as I said 32 days Post PEP I was negative I would really appreciate if you can take out some time and guide me.

    Warm Regards

  9. Dear Dr Tan,

    I had unprotected sex (insertive vaginal, I’m male) with a prostitute (white European) in London. She told me she is ‘clean’, but I started PEP 14 hours after exposure. I finished the PEP course, and I tested negative 2 weeks after finishing PEP (the doctors who prescribed PEP did the test in a lab, it was not a rapid one). Can I consider it conclusive?

    Many thanks (I’m worried)

    • No you cannot consider it officially conclusive. But honestly, you can stop worrying about HIV. Your tests are as good as conclusive (just not officially).

  10. hello doctor.
    Im from Greece…i get Pep at 36 hours..
    i have finished 28 days..
    i have tesht one month after PEP with elisa negative
    and i have another test with CMIA ag/ab after 2.5 months after PEP negative again..
    whats is your opinion can test again at 6 months or is ok??
    the latest I’ve days display a white tongue and I fear that is ASR symptom..
    thank you for your time have a nice day..

  11. Thanks Dr.Tan for your responce sir but due to anxiety I against again got tested on 101 day post exposure with third generation immunochromatograpic assay test and was negative again as from this platform I request everyone to remain faithful to one partner only how Scarry is even thought of getting HIV is that I have seen in last 3 and half months. To every brother be alert and always remain safe.

    Warm Regards

    • Thank you for sharing your experience. I am glad you are OK. I hope you can finally let go of your HIV fear.

  12. Dear Dr. Tan,

    After a burst condon with a woman (sex worker), i was put in Pep by my Doctor. I take biovir and tenofovir for 28 days. After that i done a Combo-Roche test at 30 days after my exposure (2 days after fininish PEP). My doctor said that this test at this time after exposure is very confidend, and the result should not change, but i have to retest at 2 months an three months after exposure and six months for hepatites. I also did tests for others dst’s, al clean thank god. I would like to know your opinion about the acuracy of my test, done at the time i did it. You have the greates website abou men’s and women health, and DST/HIV of all web. I whish good luck, happy and prosperity for you and your family. Greetings from Rio de Janeiro – Brazil

    • Greetings to Rio. I have never been but I heard it is beautiful. Your HIV test is as good as conclusive although officially you should still retest at 3 months. I am sure you are clear of HIV.

      • Dear Dr. Tan

        Im very happy, my test at 2 months after exposure and one month after PEP came back negative. It was a Combo-Roche Test. I know i will have to retest, but i’m a lot calm now. I would like to tank you for your help, and say that i put you name in my church golden book, for receive prayers for all your life. Thank you, God Bless You.

        • Thank you. That means a lot to me. I am glad you feel calmer. I am sure you will be well and free of HIV.

  13. Hi,

    Dr. Tan I am Garry you may be remembering me actually I wanted to update one thing that is being indicated by Goverment Of Alberta which says that 6 months post nPEP test is not required unless nPEP is extended significant enough or a person is suffering from HCV or there are chances of HIV-2 please go through the link I would really be glad if I can calm down any one who is stressed just like me it is said that 3 months test post exposure is conclusive. The link for website is http://www.health.alberta.ca/documents/PEP-Guidelines-2013.pdf

    Warm Regards

    • Hi Garry,

      Thank you for the update. It seems to me that more and more health authorities are accepting the fact that a HIV test at 3 months is conclusive even after PEP. This is very encouraging indeed. I am glad you are well.

  14. Hi Dr Tan
    Im not feel ok after PEP…
    I test 12 weeks after PEP negative with Oraquick..
    In this period I feel sick I had white tongue lymph nodes on my neck and on my armpit I sleep every day for 10-12 hours and I wake up too tired..
    I plan to test elisa 13 weeks after my last dose of elisa im scared…
    Thank you for your answer..
    Cheers from athens

    • Greetings from Greece,
      Dr Tan i have just read Nick’s message and i would like to wish him the best since i can feel his anxiety because i am currently facing a similar situation…

    • You do not have HIV. Let it go.

  15. Hi again,
    I am ready to share, in detail, my story now and ask for DR TAN’s kind advice.
    I had sex with a Thai ladyboy…I was the insertive partner but somehow in the final sex position the condom got out of my pennis and i only noticed after ejaculation -maybe 2 minutes of exposure.
    I was scared and i took the ladyboy for testing immediately in a big Thai hospital.
    Unfortunately she/he was HIV positive and Hepatitis B positive.
    I was terrified and felt like this is the end…
    I was tested HIV negative and Hep B negative.
    I was immediately (5 hours after exposure) given HIV PEP ATRIPLA for 28 days.
    At the same time i had an HBIG injection and first shot of HEP B vaccine.
    After i finished my PEP treatment my Greek doctor told me to have a 4th Generation Antigen/Antibody test 35 days -(5 weeks) after exposure which came back – NEGATIVE.
    I forgot to mention that i also had my second Hep B vaccine shot-1 month after first shot.
    Now comes the million dollar questions because i am already confused from reading the internet…
    1)Should i get my final HIV testing in a couple of days- at 3 months after exposure like my Greek and Thai doctor suggested or should i wait for another month because of PEP ?
    2)What about Hepatitis B ? Is it considered a good idea to get tested now – at 3 months after exposure or should i wait?
    3)My Greek Doctor told me that he is 95% certain that i will still be HIV negative since the negative HIV Antigen/Antibody Test i took at 5 weeks after exposure. What do you think?
    I didn’t have any flu like symptoms or other symptoms by now.
    Thanks in advance for you time and information.

    • 1. At 3 months. Both your doctors are correct. You need to trust them more. 2. Yes, test now. 3. I am even more optimistic to say you are as good as 100% negative.

      • Hi from Greece,

        I think i have good news…
        Dr Tan 10 minutes ago i had my 3 month (13weeks) post exposure results:

        1)HIV 1-2(Biomerieux):NEGATIVE 0.05…<0.25negative
        (4th generation test)
        I think this is final and i should stop worrying about HIV. Do you agree?

        2)Anti-HCV: NEGATIVE 0.06index…<0.8 negative
        Is this final for HCV? Do i need to test again?

        3)HBsAg: NEGATIVE 0.2index… <0.80 negative
        HBsAb: NEGATIVE 10 U/I … <10 negative
        I am not 100% happy about this result. Considering i had a)an HBIG injection 5 hours after exposure and the first shot of the HEP B vaccine and b)second shot of HEP B vaccine one month afterwards (2months before testing)…shouldn't the HBsAb result be positive or above 100 or 1000 U/I?
        The microbiologist who performed the test just told me that everything is ok…nothing more, even though i explained the situation in detail.
        I will be very grateful if you responded because i can not find any other doctor during the weekend and i am getting really worried.

        • I think you are fine. You could be a Hep B non-responder.

          • Dr. Tan,
            Let’s hope that everything will be ok…because my doctor in Greece has never seen HBsAb-negative 3months after HBIG and after 2 doses of Hep B Vaccine. But the main point is that i am HBsAg-Negative.
            Anyway, thank you for you help, I don’t know if you celebrate Christmas or New Years Day like Europe, but i’ll send you a postcard from Greece.

          • I’m sure you are OK. Looking forward to the postcard.

  16. Good day to you Dr. Tan,

    I’m from UK. Can you please assist me with my worries.
    On the 11th of November I had sex with a male and I was the insertive person. I used a condom and at some point the condom broke and I did not realize it. There was no ejaculation that occured. I immediately stopped once I saw the condom was damaged. The sex was for about 10-12 minutes and I am not sure at which point the condom broke.

    I panicked and went to the hospital after a few hours and was started on PEP 12hours after exposure by the registra in A&E. This is my second day on PEP.

    Dr. Tan, can you please tell me how effective is PEP when taken 12.hours after exposure? I have no idea of the HIV status of the other party and to be safe I’m treating it as HIV+. I am very very very worried on how successful PEP will be. Can you please advise me and I apologize if I am troubling you here. My baseline HIV Result was negative. When cam I know if I am out of this danger zone?

    Please advise.

  17. Good day to you Dr. Tan,
    I’m from UK. Can you please assist me with my worries.

    On the 11th of November I had sex with a male and I was the insertive person. I used a condom and at some point the condom broke and I did not realize it. There was no ejaculation that occured. I immediately stopped once I saw the condom was damaged. The sex was for about 10-12 minutes and I am not sure at which point the condom broke.

    I panicked and went to the hospital after a few hours and was started on PEP 12hours after exposure by the registra in A&E. This is my second day on PEP.

    Dr. Tan, can you please tell me how effective is PEP when taken 12.hours after exposure? I have no idea of the HIV status of the other party and to be safe I’m treating it as HIV+. I am very very very worried on how successful PEP will be.

    Can you please advise me and I apologize if I am troubling you here. My baseline HIV Result was negative.

    When cam I know if I am out of this danger zone?
    Please advise

  18. Xin chào Bác sĩ Tân! Em là người Việt Nam

    Em xin phép viết bằng tiếng Việt Nam vì em không thông thạo tiếng Anh. Đọc được trang web này là em nhờ google dịch lại.
    Nguy cơ của em là quan hệ tình dục đồng tính nam (gay) với người nhiễm. sau đó uống PEP sau 48 giờ. Sau khi ngưng PEP 9 ngày em có xét nghiệm bằng DETERMIN HIV 1/2, kết quả Âm tính. Vậy em hỏi là như vậy khi xét nghiệm 3 tháng sau kết quả có khả quan không. em chân thành cảm ơn.
    Xin bác sĩ Tân trả lời thắc mắc dùm em qua Email của em được không ạ. Em cảm ơn

  19. Hello Dr. Tan! I was the Vietnam

    Hello Dr. Tan! I was the Vietnam
    NOVEMBER 15, 2013
    Your comment is awaiting Moderation.
    I’m allowed to write in English Vietnam because you are not fluent in English. Read this website through google translate is children.
    The risk of a child sex gay (gay) people with HIV. then taking PEP after 48 hours. After 9 days I have stopped PEP tested by determin HIV 1/2, Negative results. So I asked the same when tested 3 months after the results are not satisfactory. thank you.
    Dr. Xin Tan Dum answer your questions via email are not you, sir. Thank you

    • You tested negative for HIV 9 days after completion of PEP. This test is very indicative but not conclusive.

  20. Hi dr its been two months after busted condom with a hiv positive female. I started the course of pep after 30hours. I did a rapid test it came out negative. My question is how many months must I test for it to be conclusive. I live in South Africa where we have a high number of hiv infected people.thank u for your time.

    • Your test is already as good as conclusive. Most guidelines now say 3 months. Some still say 6 months. You have to see what your local doctor says.

      • Hi dr tanx once again for your experience and hard work. now it’s 77 days of negative hiv testing. I know i must wait for 3 months for the test to be accurate.I have a pain on my neck but no swollen lymph nodes or glands, my tongue also has 2 sores at the back of my tongue. maybe it’s Anxiety. have you seen 77 days of negative turning positive.

      • Hi, dr Tan.i would like to thank you for your encouragement. I have completed 3 months after pep and the results were negative.

      • Hi, dr Tan.i would like to thank you for your encouragement. I have completed 2 months after pep and the results were negative. now it’s 3 months after exposure. Merry Christmas enjoi .

  21. doctor
    i had condom breakage 6 months ago (exactly on 7th june 2013 at 3pm ) i started PEP on 10 the june afternoon 1 pm. PEP got over after 28 days. i tested negative 3 months from exposure (which was 2 months from completion of PEP). then again tested negative 6 months from exposure (5 months from PEP completion). am i out of HIV risk? please reply me. i am from india. thankyou.

  22. hi doc. i have condom breakage with girl and after 16 hr.i took pep. after 3 weeks post pep i get antibody test negative.is this test is conclusive dr. please help me..really worried..plz dr.

  23. hi doc.i have had 3 weeks post pep antibody test negative. how conclusive is this test. help me out. am really worried.

  24. Hi Dr. Tan,

    Good day to you and thank you in advance for taking time to answer my question. 7 weeks ago I had a male to male sexual encounter where I was the insertive party. I wore a condom but sometime during the 10-15 minutes activity the condom broke and I didn’t realise it. The hiv status of the receptive party is unknown.

    I started PEP within 15 hours of potential exposure. I was told to take 1Truvada & 1Kaletra in the morning and 1Kaletra in the evening. During the 4 week period I kissed about 3 evening kaletra intake by a few hours (once 60 minutes and twice about 90-120 minutes), will this be a problem.

    It has now been 3 weeks since I completed my PEP treatment (9/12/13 being the last day) when can I get myself tested and with me missing the intake of tablets in time three times, will that be a problem?

    I am extremely anxious at the moment. Please advise Dr.

    • You can test now which will be very indicative and test again at 3 months post exposure to be conclusive. I do not think missing 3 doses made much difference.

  25. Sir I had sex with positiv prostitute
    My condom broke In d end
    I saw and aborted the sexual relatin

    I’m very scared I could get infected ?


    hi Dr Tan,
    on 15th December I was exposed to a hiv + woman with cd4 847 and viral load of 1700. I was very drunk and we had sex for 5 minutes and it was un-protected. I only realized that she just ended her period and had traces of blood, the sex was not rough at all as her vaginal was very large and lubricated. after the sex I just blacked out, and woke up 4 hours later to rinse of the fluids. 50 hrs later I asked her about her status and tols me she hiv +. so I started pep at exactly 60hrs. 3 days after pep I had fever and night sweats and nausea and diarrhea. pep treatment will e done on the 14th of jan 2014. doc I am really worried. I dnt even know what to ask you.

    • There is nothing much for you to do now except take your pills regularly and re-test after you have completed the PEP treatment.

      • CASHEW NUT

        hi drtan,

        I took a hiv rna test and just awaiting results. thank you for response.

        • cashew nut

          Hi Dr Tan,
          I have just received results from hiv rna test,
          HIV Ag/Ab 0.78 S/CO NON-REACTIVE
          HBsAgQ2 0.21 S/CO NON-REACTIVE
          Anti-HCV 0.07 S/CO NON-REACTIVE

          MY QUESTION IS, is an hiv rna test affected by pep treatment?

  27. Hi Dr Tan,
    I took PEP after 60 hours and completed the treatment. During and after that I had all kind of symptoms but no fever. I tested negative 8 weeks and again 12 weeks after exposure following a 4th generation lab test. The girl was a black female with unknown HIV status. My question is do I need to test again at 4 and 6 months post exposure as there may be a risk of HIV-2 infection or is my test conclusive? Thanks, Ted

    • That is rather controversial. Most PEP guidelines still recommend testing up to 6 months although some have corrected this down to 3 months. In my opinion, 3 months is enough.

  28. Dr, New York brand new PEP guideline:


    They said just three months after exposure for a conclusive result! It seems more and more guidelines are down the time for a conclusive result!

    • Thank you for sharing. This was actually published last year. But you are absolutely right to say more and more people are realising the fact that PEP does not extend the testing window period.

  29. Hi Dr. Tan:

    I am a 30 yo male who had a few minutes non-protected insertive vaginal sex with a HIV+ woman (I didn´t know she was at that moment).

    68 hours later I went to hospital and started PEP (Kaletra+Truvada) for 28 days with 100% adherence.

    16 days after PEP (47 days after exposure) I had two tests in hospital:

    – Viral Load Test: non detected
    – Antibodies: negative

    My doctor says I must wait until 3 months to get conclusive results but she has told me that viral load test is very accurate so I can be confident that I am fine.

    What do you think? Honestly, can I take these results as conclusive and forget this nightmare?

    Thanks a lot in advance.

    • Hi, honestly I am already quite convince you haven’t got HIV. however the most conservative PEP guidelines would recommend a repeat test at 3 months. Please continue to see your doctor for follow up.

      • Hi Dr. Sim:

        Thank you very much.

        I had another Antibodies Test 59 days after exposure(28 days after PEP) and it is negative.

        Have you ever seen a 2 months negative test turning positive at 3 months?

    • Hi Marcos,
      remember not every exposure leads to transmission of hiv. so stop stressing yourself. relax.

        • Thank you very much audi s4 and Dr Sim. I will try to relax :-)

          • I tried to relax but I could not so I had a blood rapid test 10 weeks post exposure (38 days after pep): NEGATIVE

            Now I have 2 questions:

            – Should I wait 2 more weeks to get conclusive results?

            – 12 weeks post exposure is conclusive or should I wait 12 weeks after PEP?

            I ask it because some guidelines say it is 12 weeks after exposure (New York or Australia), other guidelines say it is 12 weeks after PEP (United Kingdom) and other guidelines recommend 6 months after exposure.

            Than you very much once again.

  30. Hi Doctor,

    I had drunken unprotected sex with a Thai girl, status unknown. I recieved PEP treatment of Truvada at 30hours and completed 28day regime without interruption.

    tested PCR at conclusion of PEP which was negative, then 3 separate P24 AG/AB 4th generation tests at 3, 5 and 8 weeks post pep. all negative.

    can i assume confidently now that i have nothing to worry about? The only reason I doubt it is that I have had recurrent sore throats for up to a month or more.

    any reaponse or detail would be most appreciated.

    kind regards,

    • I think for all practical intents and purposes your do not have HIV. However, even the most conservative of protocols will call for a repeat HIV test at 3 months post exposure when there is PEP use.

  31. Hellp Doctors,

    I’ve done the follow test after PEP

    4 weeks (just after the completion of pep) Combo Test Lab
    8 weeks (4 weeks after pep) Combo Test Lab
    12 weeks (8 weeks after pep) Combo Test Lab
    16 weeks (12 weeks after pep) Combo Test Lab
    20 weeks (16 weeks after pep) Elisa 3ª generation lab test.

    All the tests are negative, my doctor said i dont need more tests. I was fine, but then i see the CDC guideline for 6 month test, and become worry again… Thank you for your time doctors!

  32. Hi Dr Tan and Dr Sim,

    I would like to ask what kind of test do you prefer to use on your pacients that took pep. 3 or 4 generation?

  33. Thank you doctor
    So do you think i M free of hiv?

  34. Dr. Tan

    Greetings from Ecuador!
    I need your expert advice. I had an HIV exposure on December 31 2013. I was fooling around with a guy, and penetrated him without a condom for less than 5 minutes (no ejaculation)but stopped because it hurt him, and then we continued fooling around and kissed for a while. I was unaware of his status and so was he. Unfortunately we fooled around again on January 11 at around 1 AM I penetrated him again this time for around 5 minutes again and stopped because it hurt him again. Then he penetrated me for around 5 minutes. (No protection, I know this is really stupid of me, I protect myself but I trusted his age because he is really young. Shame on me) I am 28 years old, he is 19. I stupidly trusted the fact that he was young. So the next day I took him to take an HIV test with me. I was negative and he was positive. So i thought for some minutes. Since the first time I penetrated him and I am circumsized and it was for a very short time, I had a good chance of not having acquired HIV. So I took the second time we had sex as my possible exposure. So I started PEP on January 12. and went on for 30 days. I had no problems finished PEP. No major side effects, a little dizzy two or three days. After PEP they checked my liver and my kidneys and thank God they were fine.
    So I´ve had various HIV tests because of my anxiety and guilt.

    – I had a fourth generation ELISA after exposure (January 11) in a private lab and it NON REACTIVE.

    – Then a third generation in the hospital (January 12) and it was NON REACTIVE as well.

    – Then I had a fourth generation ELISA (January 31) while still on PEP it was NON REACTIVE.

    – Then I had a third generation at fourth week after exposure and after I finished PEP, it was also negative.

    – Then I had a third generation test at fifth week (one week after PEP), also NON REACTIVE

    – Then I had a fourth generation test at sixth week (two weeks after PEP), also NON REACTIVE

    – Yesterday I had a fourth generation test at seventh week (two weeks after PEP), also NON REACTIVE.

    Please Dr. Tan, give me your comments and advice. I am quite anxious and nervous. Thanks for your page, it has helped me since day one.


    PS. I have been boosting my inmune system with vitamins B and C. I also take an ecuadorian product called BIRM which is a natural product/dietary supplement that supports the immune system and balances the defenses of the organism. Nominated for the Nobel Prize of medicine some years ago. http://www.ecuabirm.com/site/index.php?option=com_content&view=article&id=1:birm&catid=1:latest-news&lang=en that improves your inmune system. So if you have a great inmune system, your body makes antibodies faster. My blood tests have come out great.

  35. Dr. Tan

    Sorry I posted the comment twice, but the first comment had a mistake.

    Greetings from Ecuador!
    I need your expert advice. I had an HIV exposure on December 31 2013. I was fooling around with a guy, and penetrated him without a condom for less than 5 minutes (no ejaculation)but stopped because it hurt him, and then we continued fooling around and kissed for a while. I was unaware of his status and so was he. Unfortunately we fooled around again on January 11 at around 1 AM I penetrated him again this time for around 5 minutes again and stopped because it hurt him again. Then he penetrated me for around 5 minutes. (No protection, I know this is really stupid of me, I protect myself but I trusted his age because he is really young. Shame on me) I am 28 years old, he is 19. I stupidly trusted the fact that he was young. So the next day I took him to take an HIV test with me. I was negative and he was positive. So i thought for some minutes. Since the first time I penetrated him and I am circumsized and it was for a very short time, I had a good chance of not having acquired HIV. So I took the second time we had sex as my possible exposure. So I started PEP on January 12. and went on for 30 days. I had no problems finished PEP. No major side effects, a little dizzy two or three days. After PEP they checked my liver and my kidneys and thank God they were fine.
    So I´ve had various HIV tests because of my anxiety and guilt.

    – I had a fourth generation ELISA after exposure (January 11) in a private lab and it NON REACTIVE.

    – Then a third generation in the hospital (January 12) and it was NON REACTIVE as well.

    – Then I had a fourth generation ELISA (January 31) while still on PEP it was NON REACTIVE.

    – Then I had a third generation at fourth week after exposure and after I finished PEP, it was also negative.
    – Then I had a third generation test at fifth week (one week after PEP), also NON REACTIVE

    – Then I had a fourth generation test at sixth week (two weeks after PEP), also NON REACTIVE

    – Yesterday I had a fourth generation test at seventh week (three weeks after PEP), also NON REACTIVE.

    Please Dr. Tan, give me your comments and advice. I am quite anxious and nervous. Thanks for your page, it has helped me since day one.


    PS. I have been boosting my inmune system with vitamins B and C. I also take an ecuadorian product called BIRM which is a natural product/dietary supplement that supports the immune system and balances the defenses of the organism. Nominated for the Nobel Prize of medicine some years ago. http://www.ecuabirm.com/site/index.php?option=com_content&view=article&id=1:birm&catid=1:latest-news&lang=en that improves your inmune system. So if you have a great inmune system, your body makes antibodies faster. My blood tests have come out great.

    • Hello George. Greetings to Ecuador from Singapore. Thank you very much for sharing your story in such detail. I think all of us can learn a good lesson from this: Youth is no protection from HIV. Now on to your case and the good news. I think based on all the tests you have done, you are as good as free from HIV. Officially you will need to test till at least 3 months post exposure (your local guidelines might say 6 months, please verify this with your doctor). However, practically speaking you are already out of the woods. Stop worrying. Stay safe and stay healthy.

      • GEORGE

        Thank you Dr. Tan for your response. It sure does calm me down more. I will of course test at 3 months and at 6 months. But if I remain NON REACTIVE at 3 months, I would so breath calmly again.
        I would like to thank you and your partners for keeping people aware and updated. It helps people like me, scared behind a laptop because we feel guilt and shame for being so irresponsible. Please people use condoms. Next Friday is my 8th week post exposure test. I hope I am NON REACTIVE.

        One side question. I read in your blog that you have had one PEP failure. I’ve read that story several times, but can’t find how long after PEP completion did Mr. M tested positive for HIV. Was it right after completion of PEP?

        Thank you in advance. God bless you and your team.


        • Timothy

          Dr. Tan did this test right after the course of PEP. He said this at another forum.

        • Yes it was at 4 weeks post exposure (immediately after completion of PEP).

          • GEORGE

            Thank you Dr. Tan and Timothy for your responses.
            By the way I got the results back yesterday for my eight week, it was non-reactive thank God.
            Have a wonderful day!

          • Happy for you. Hope that takes a weight off your mind.

          • Dr Tan,

            My last ELISA test was at the beggining of week 11 post exposure and it was non reactive. I am waiting for the end of week 12 so I can have my 12 week post exposure test.
            I have one question, 4 days ago I started having a HORRIBLE headache that has lasted this 4 days. Do you think this can be related to ARS or HIV? I have had no fever, no rash, no swollen lymphnodes, diarreah, I have been a little dizzy (Caused by the headache that usually goes down when I wear my glasses) but I am extremely worried about this. Can you please tell me if headache is a symptom of ARS? Can you please also tell me until when can ARS symptoms occur? I have read that if ARS doesn´t happen until week 6, it won´t happen. And if any symptons occur, it is not ARS or HIV, it is something else. Is this true? Please help me, this Friday is week 12 and I am really nervous.

            How conclusive do you think my 10 week post exposure (6 weeks after pep)non reactive 4th generation ELISA was?

            Thank you

          • ARS symptoms do not happen after 6 weeks. Stop scaring your self.

          • George

            I just received my ELISA 4th generation 5th day of week 12 none reactive. Even my headache went away. Thank you Dr. Tan. I know I bother you too much.

          • The important thing is that you do not have HIV. Stay safe and stay healthy.

      • GEORGE

        Here in Ecuador I get the results on the same day. Fourth generation ELISA (combo test) P24 Antigen and HIV Antibody. I will get the test this Friday morning or Saturday morning and tell you about it. Thank you again sir.

        • Hi George

          I live in Ecuador and want to get tested. I had unprotected sex with a girl which I am unsure of her status. I do not want to wait the full three months as it gives me anxiety.

          Can you tell me where I can get the RNA test? or any test that would show results after 10-12 days?

          • I’m sorry. I am not familiar with the HIV testing facilities in Ecuador. Anybody reading this who has some info to share on HIV testing in Ecuador please help.

  36. Dr.Tan, i wish to remember my history an to thank you. My name is John and i’m brazilian. I have an accident with a burst condom with a sex worker, after that i panicked and look for PEP. After PEP, i spent a lot of money and get a consult with the greatest infectologist at my country, Esper Kallas, he is member of the United Nations Aids Program and one of the directors of the vaccine program of WHO. He said that 4 weeks after pep with a 4 generation it’s enought, you too said me that this tast was as good as conclusive. But i just calm down with my 4 Generation test six months after exposure, i receive this result few minutes ago, negative thank God. I return to thank you, thank your pacience, your kindness in respond all these questions from people that you even know, with any payment. You have GOD in your heart, and i will pray for you for the rest of my life. If one day i go to your country, i will go to your clinic and get a consult with you to give you a hug and thank you personally. I wish world have more doctors like you, you really honor MEDICINE!

    • Thank you very much for your kind words John. I am very happy and honoured that I had the chance to make a positive impact on your life.

  37. worriedSA

    Hi Dr Tan,

    been reading your site and your comments are assuring. thanks. Dr tan I had sex with a massage therapist in Thailand on 1 January 2014, I took pep at 57 hours for 27 days ( skipped the last 3 tablets) I did the following tests

    all after exposure
    week2 : PCR RNA and 4th generation elisa _ negative
    week 3 : PCR RNA and 4th generation elisa – negative
    Week 4 : 4th generation elisa – negative
    Week 5 : pcr rna and 4th generation elisa – Negative.
    week 6 : PCr rna and 4th generation elisa – negative
    week 8 ( 4 weeks after pep): 4th generation elisa – negative

    the lab says that the test results are 100 % accurate within 2 to 6 weeks using 4th generation”

    if you had to attach a number to the chances that my results will change what would you say from your personal experience ? 1 out of how many will have a changed results ?

    pls respond


  38. worriedSA

    hi Dr tan,

    I had sex with a massage lady in Thailand, I sued condom but it slipped off and I noticed after 3 minutes,

    I did a 4thgeneration elisa test at 8 weeks after exposure and 4 weeks after pep, all negative.

    in your own experience if you had to attach a number to it , 1 / (out of how many) will see a changed result 4 weeks after pep ?

    thanks for the advise you give on your site, you are a beacon of light to those in despair.


  39. worriedSA

    Hi drtan,

    sorry I mean my test at 10 weeks post exposure and 6 weeks post pep was negative.

    here is a copy.

    HIV 1/2 Ab + P24 Ag *
    The negative HIV Ag/Ab result should be interpreted in
    conjunction with the patient’s clinical picture and history
    of possible exposure to HIV.
    The HIV Ag/Ab test is 100% sensitive in detecting HIV
    infected patients that are not in the window period. The
    window period (time before antigen or antibodies are
    detected) varies between 18 days to 6 weeks).
    The negative HIV Ag/Ab result excludes the diagnosis of HIV
    infection in all patients that do not have a history of
    exposure during the 18 days-6weeks before the test was
    This laboratory uses the Combo 4th generation ELISA test as
    1st line screening assay.

    For consultation, contact Clinical Microbiologist At Local Laboratory

    H=High, L=Low, *H=Critically High, *L=Critically Low
    File [ ] Phone Patient [ ] Appointment [ ] Prescription [ ] Draw File [ ]

    • For post PEP most guidelines still say test at 3 months. So although I can say you really do not need to worry about HIV anymore, officially you still need to be retested at 3 months.

  40. worriedSA

    hi doc, 3 months after exposure or 3 months after completion of pep ? what would you say are the chances that my result and 10 weeks post exposure will change ?
    1 out of ?
    thanks for response, you are a legend

    • Dr. Tan and recently updated guidelines say that 3 months post exposure after PEP is considered conclusive when a 4th Generation test is used, unless yo have Hepatitis, organ transplant, weak inmune system for certain reasons or are going through chemotherapy. I am going through the same here been worried, my exposure was January 10, 2014, with the difference that the guy I had sex with turned out to be HIV positive. I am in my 9th week (5 post PEP) and last test on March 07 was non reactive. I hope it remains like that. Dr. Tan has been a real support.

  41. stressedOut!

    Hello Doc,
    I recently had a condom break having sex with a chick in Thailand. I didnt realize it had broken untill I pulled out. I immediately asked if she had hiv and she replied no. I went to local patong hospital within 20hours and got a full blood work done.
    Cmia hiv test came back non reactive. And so did all the other tests.
    Now the doc didnt speak English well and I wouldn’t understand if it came back negative why do I need to take all these tablets? We couldnt get anywhere due to language barrier so what I concluded it was just for precaution. I took them for first few days but made me really sick so cut back to 1 lot a day. Its now day six and im wondering how accurate that test really is after 20 odd hours? Plus what is the odds of getting hiv of a chick to start with? Lets say she is hiv positive.
    Should I go see my doc now I am back home for another test that maybe more accurate?
    Look forward to your reply and thank you very much for your time in advance.

    • The HIV test was just to establish that you do not have a chronic HIV infection. It tells you nothing about the encounter. The doctor started you on PEP because you do not have an established HIV infection and you are at risk. You need to complete your pills and stick to your regime. If not you might as well don’t take them. Taking another HIV test now is useless.

  42. Well, after I read what I wrote I even confuse myself a little bit because I wrote it incomplete. Newly updated guidelines say that 3 months post exposure and 2 months after PEP can be considered conclusive with normal conditions of your body. Some countries like mine still say 6 months, but those are the Public Health guidelines here in Public Hospital that test with rapid tests, I go to a private institution where they have fourth generation ELISA. Hope I helped you.

    • worriedSA

      HI George, do you have any info if HPV co infection can delay sero conversion beyons 3 months ? or is a 4th gen elisa test considered conclusive indefinably ? have you got any fact on that ?

      • For what I have read, Hepatitis delays seroconversion, test results for HIV can be conclusive in six months when someone tests positive for HBV or HCV. (HCV being the strongest one BUT the hardest to transmit, only blood to blood)
        For HPV I am not sure. Some people say it does, some people say it doesn´t, the main reason is that HPV has so many strains, that not even the vaccine protects you from all the HPV types.

        • worriedSA

          ok thanks, I also read they say its on HCV but not with a co infection, only if they had HCV before HIV exposure. how you holding up ? how many weeks u on now ? I have 12 days to 3 month marker.

          • Today I enter week 10. I just had a full blood test and I am fine in hematology and enzymes. Also had VDRL and none reactive. Tomorrow I get this week´s test results for HIV. Hope they are still non reactive.
            It is crazy how I am calm most of the week, but get soooo stressed out when I am waiting for the test results. Eventhough Dr. Tan and some Doctors here in Ecuador tell me everything is fine, that I don´t have HIV, I worry I am one of those that seroconvert later on. I guess its mostly because I feel stupid, because I don´t have any of the things that delay seroconversion. But then again, there are so many theories on the internet that drive me crazy. I know I shouldn´t be reading stuff on the net, but it´s like an addiction. I keep looking for stuff that make me feel better, but find all sort of stuff. And I little feel my heart will stop when I am waiting for results! I even analyze facial expressions of the people when they are looking for the results and have panic attacks. I am so scared IT IS RIDICOLOUS. I read how people can calmly wait for 12 weeks without testing… I AM GOING TO RUN OUT OF BLOOD FOR TESTING EVERY WEEK. ugh… I have to stop.

          • You need to calm down. Don’t let the anxiety itself become a problem. Is it so hard to accept the fact that you do not have HIV? Accept it and be happy.

          • This week also non-reactive :) thank God!

          • One more step towards freedom.

  43. worriedSA

    HI Dr tan,

    does HBV delay seroconversion.? does HAV HBV or HCV delay seroconversion ?

  44. Hi Dr. Tan,

    Thank you so much for your generous service. You are a great person.

    I was the insertive partner in sexual activities with another man unknown of his HIV status. I used a condom but realized it broke after 3-4 minutes of insertive intercourse. I started PEP 48 hours after the event. I was tested with the antibody testing, today, which was one day after PEP (33 days post exposure). The doctor said that the test results for the antibody use ELISA technology and are rather accurate. However, I am reading online that you must wait 4-6 weeks POST PEP (so 8-10 weeks post exposure) to get a test and that PEP will not give accurate results.

    What are your thoughts given I just took an antibody test (ELISA, whatever that means) just one day post-PEP and 33 days post exposure.

    Thank you!


    • I absolutely agree with your doctor that the ELISA test you did is very very accurate. However, all PEP guidelines will recommend retesting at at least 3 months some even say 6 months post exposure.

  45. Anxiety

    My case is a little compicated, so sorry to trouble you.

    I(male) had unprotected receptive anal sex, receptive and incertive oral sex with an HIV+ gay man 5 months ago(29/10/2013). He was likely on acute infection period with high viral load. And definitely I was extremely in high risk.

    I took PEP about 12hrs after exposure(Lamivudine+Zidovudine+Kaletra, bid), and finished the 28-day course except that I MISSED one dose of all the three drugs at the second day night.

    I got a continuous 4th geneation HIV ag/ab test since 5 weeks after exposure until 12 weeks, and all the test were HIV non-reactive. And on 13 weeks(25/12/2013) I only took a 4th generation ELISA test without P24 test, non- reactive.

    Then on 22/12/2013, I had receptive oral-penis and receptive oral-anal sex with an another gay man. Then on 24/12/2013 he took an rapid HIV test and turned out to be HIV+. Since my anal had a 5mm*1mm breach when he performed rimming on me and I was not sure about his oral health, I took PEP about 55 hours after exposure with 28-day. I got an HIV 4th generation Ag/Ab test at 4 weeks(immedietely finishing the PEP) and 8 weeks(20/3/2014) after the exposure, and both non-reactive.

    At week 4(22/2/2014), I took a CD4/CD8 test.The result was so indicted for HIV acute infection(CD4 459, CD8 1089, ratio 0.42) which put me in despair.

    My question were as follows:

    1.I got an HIV-negative using 4th generation Ag/Ab test about 5 months after the first exposure. But at first month(missing one dose) and 4th month I took 2 times PEP, did the second intake of PEP retarded the window period of the first time exposure, since it was extremely in high risk. Could the result be conclusive for the first time exposure?

    2.I got an HIV-negative using 4th generation Ag/Ab test about 8 weeks after the second exposure. Since the second exposure was actually low risk, could the 8 week result be conclusive?

    3.Did the CD4/CD8 test make sense since HIV Ag/Ab were negative? Or if the high CD8 count was caused by HIV virus, the 4th generation Ag/Ab test should have had a positive result after 4 weeks? Could I understand like this?

    Really looking forward for your reply!!!

  46. Hello Doctor, hope you will answer my queries,

    On 23rd Jan 2014 had unprotected sex with a lady, started PEP (zidovudine 300) within 40 hours of exposure but stopped after 4 days as it had severe side effects on me. On 10th mar 2014 had HIV MEIA test on my partner and it came NON REACTIVE. Again on 26th Mar 2014(at 62 days of exposure) I myself had HIV MEIA test and it came NON REACTIVE too. I would definitely like to test on 90 days of exposure. My question is that will 4 days of pep effect my HIV test results on 62 days and 90 days.

  47. may7788


    • 1. 艾滋病抗体测验在12周或3个月进行都没差别。 2. 已经非常准。但是应为你服用了PEP, 你还是需要等到暴露后3个月再测试。

      • may7788



        • may7788


        • 你下周的测验是百分之百决定性的。如果你下周测验的结果是陰性, 请别再測試了。

          • may7788


          • 没差别。

  48. Hello Dr. Tan

    i have completed my PEP on 2014/3/11.

    5 days later i took a rapid test using determine hiv 1/2 which is said to be as accurate as lab-based 3rd generation ELISA test and it came out negative.

    I know it’s not officially conclusive, but i want to ask how confident can i be?
    Thank you for your kind work!

  49. Hi dr,

    I had unprotected sex with my partner in feb this year but it only lasted like a minute and then I stopped him. Again in march the 27th we had unprotected sex, the following day I saw in his drawer an hiv report that his hiv positive. I then rushed to get dr to get pep, so i am currently on pep and my question is what are the chances that I might test + post the pep treatment considering that in feb I didn’t go on pep….reallly worried!!!

    • The risk of contracting HIV from each exposure of unprotected receptive vaginal sex is about 1 in 500 to 1 in 1000. There are many other factors that can change this risk like whether or not he is on ART, cuts, abrasions, ulcers, tears, sores, concurrent infections etc. Your doctor should have done a HIV test for you before starting the PEP. A negative test at least gives you a good indication that you were not infected during your Feb exposure.

      • Thanks dr for your response and time. I had done an elisa test in feb and my results where – and before I was given the pep I did a rapid test which was also -. So I am really worried about the chances of my results changing to + post the exposure I encountered in march now that you have answered me for the feb encounter. I am really struggling to do anything due to stress.

  50. Hi Dr
    I would like to thank you about your good work. and you have the most accurate data information about when to test after using pep medication.
    I was exposed to a hiv positive female 6months and 10 days ago. Dr tan calmed me down when I was anxious with no hope. He told me to test after 6 weeks after using pep medication and again 3 months. While others told me I should wait for 6months of misery, 6months it’s like 6 years of pain.
    Thanks a million Dr, I did as you told me today I’m hiv negative, I don’t believe it but the test is confirming. without you I was lost. Please continue with your marvellous work to save human beings.

    • I am glad you are well. Thank you for appreciating what we do.

  51. Hi dr

    3 months ago i had a sexual exposure through unprotected intercourse. 48 hours late i started the three in one pep regimen which i completed 28 days later. The next day i took a rapid antibody test which came back negative. 9 days later I took RNA test which also came back negative. 17 Days after completing the pep I took another RNA test which came back negative.Yesterday was the three month mark after exposure and did a rapid antibody test which came back negative. Do you think these results are conclusive?if not whats the confidence i should have in all my tests done? And is there any test I can perform NOW(such as another RNA test) that will allow me not to have any further tests in the future.

    Thank you in advanced for your advice

  52. Hello Dr. Tan

    I’m from the US. I had receptive anal sex with another man. We used protection but the condom ended up rupturing and we didnt find out until after he came inside of me. He came a lot and I freaked out because he is known to be HIV+. I quickly went to the ER and got on PEP (Atripla) for the 28 days. As soon as I was done, I took an Oraquick test at 4 weeks post exposure and that came back negative. I then waited and took another Oraquick test two weeks later (6 weeks post exposure) and it also came back negative. What are my chances that my 12 week test will come out negative as well? Thank you so much for all your hard work!

    • I think the 2 OraQuick tests that you have done are already very indicative. Personally I think there is no chance that your test at 12 weeks will be positive. I think you have well and truly dodged this bullet. That said, please still go for your 12 weeks test.

  53. hi dr Tan

    It would be greatly appreciated if i got your opinion on my situation. I had a sexual encounter about three months ago. I went on pep 48 hours later and completed the 28 day course. I then had an antibody rapid test done the following day of completing the pep. Yesterday was the 3 month mark after the exposure (2 months after) pep and I had an hiv pcr rna test as well as an antibody rapid test. Would you say my results are conclusive?If not, what are the chances that im clear of hiv and could you tell me if there is anymore tests I can do now to ultimately stop me from testing further down the line.

    Thank you in advanced for your advice

  54. ScaredEc

    Hello Dr. Tan,

    Greeting from Guayaquil, Ecuador. I saw your page on a HIV blog here, where they recommended you as one of the best.

    I am extremely worried and people say I am crazy.
    I am a 28 year old gay male, and I had sex with a 25 year old gay male. On April 12/2014 I was the insertive partner (I was top) we used a condom for sexual intercourse and just when we were about to finish, we changed positions so i had to take my penis out and insert it again. We had sex for around 3 or 4 minutes more until we were done.
    It wasn´t until i pulled out my penis at the end that I realized that the condom had broken and I came inside of him.

    We both worried but I had just had a 4th generation ELISA on April 01/2014 and it was Non Reactive so the guy calmed down but his last HIV test was on January 2014 (around 4 months ago) he told me he always protected himself and had never had a broken condom in the last year. We went to take an HIV test but the results came back next day, so after that I went to a Hospital and started PEP (ATRIPLA)inmediatly at 3 PM before 20 hours of exposure and they told to wait for his results.
    His 4th generation elisa results came back Non Reactive and mine did too. But before we got the results, I started thinking “what if he is in window period and he has a false negative” I have known the guy for MONTHS and we have had sex a few times but I just got anxious because of condom broke and we were not exclusive. So when I received the test results NON REACTIVE, they did not calm me down. Of course the hospital took me out of PEP and said that since he was HIV negative I didn´t need to do PEP and the fact that we used a condom and it broke at the end, was safer because the penis did not had any friction and was intact (I applied alcohol after I realized the broken condom and it didn´t hurt so I had no laserations) They examined his throat and his glands and said that he had no indications of being in the window period. But I was still quite worried. Of course I started touching my lymph nodes every 5 minutes and overeacting over anything I felt, and 3 days after condom broke, I started feeling two lymph nodes on my neck on the both sides and I got so worried I even felt nausea when I found out my lymph nodes were swollen.

    Is it possible to have this sympton only 3 days after possible exposure? is it possible to have any ARS sympton after 3 days of exposure? is it possible that I created this swollen lymph node by stress or by touching it? Am I crazy? I am a bit hypocondriacal I must admit, but I can´t seem to calm down.

    A friend of mine, she is a Doctor, and she tells me I am somatazing symptoms; that it is impossible that I have ARS because the guy was non reactive and even if he was in window period, which she thinks it is unlikely because of his examination of throat and lymph nodes, it is still to soon for symptoms.

    Can you please give me your opinion Doctor Tan. I am desperate.

    • First of all I think you got your dates wrong. But never mind that. I completely agree with your doctor friend that your symptoms are probably born out of your anxiety. It is impossible to have symptoms of HIV infection 3 days from the exposure. In all likelihood you were not exposed to HIV in the first place.

  55. ScaredEc

    I double checked dates, they are corect.

    January 2014 he had his routine HIV test and was NON REACTIVE.

    April 01, 2014 I had my routine HIV test and was NON REACTIVE..

    April 12, 2014 Condom broke.

    April 13, 2014 We both took 4th generation HIV test and it was NON-REACTIVE.

    Thank you for your answer Doctor. I don´t usually get flu like symptoms and I had the flu shot in January. I have had a sore throat and the tonsils swollen since the incident. Are tonsils lymph nodes? I have no other symptoms. Do ARS symptons come all together or can someone just have one or two?

  56. worriedSA

    Hi Dr tan,

    hope you have been well ?
    Dr tan I did my test a 5 months after exposure and 4 months after PEP it was negative, can I consider my results conclusive ?? pls advise, take care

  57. worriedSA

    I used a 4th generation elisa test.

  58. beebz


    I was just wondering the possibility of ARS symptoms occurring after 28 days of PEP completion? Would they already have happened by now or would PEP have halted seroconversion until after the PEP has been completed?

    I’m freaking out a bit. I’m receiving my test results next week, 28 days post exposure, but when my blood was drawn, I still had one more dose of PEP left.

    Will still being on PEP have an effect on these results?

    If I could please have your professional opinion I will be so grateful.

    • drtan

      Whether or not ARS develops really has nothing to do with being on PEP. There is a lot of theory on PEP affecting the HIV testing window period but none of this has been proven. In my own experience, a HIV test immediately following the completion of PEP is extremely accurate.

  59. Hello Dr.Tan,

    I just finished my 28 days PEPs today with combination of Kaletra & Combivir. I took PEPs at around 68 hours post exposure.

    My story was, I had protected vagina intercourse and unprotected oral sex (I am receiver). I have few questions:

    1. Was my risk of getting HIV infection high?

    2. When should I get my test for HIV?

    3. I am uncircumcised. Will this adding more risk to my condom usage?

    I hope I can get answers soon. And million thanks.

    • drtan

      You obviously did not take those meds from us. Those are the old regime and honestly the US CDC now even recommends against one of the components in these meds for use in PEP. I suggest you go back to the doctor who gave you these meds to answer your questions.

  60. worriedsick123

    Dear Dr,

    I would like to ask you my theoretical risks regarding my story with a girl of unknown status.

    1. I had unprotected oral sex (bj) for about 10 secs.
    2. I properly used the condom for vaginal sex, but then lost erection because I was drunk, so I took it off. Then I masturbate myself to get an erection back and put the *used* condom back on. *There I am not sure if I put back on the wrong side.* Upon realizing it is not good to reuse the condom, I took it off after not longer than 3 seconds.
    3. Then I took out a new condom and had vigorous sex for maybe 15 mins.

    Can you tell me my risks?
    For scenario 1, am i at risk?
    For scenario 2, i am really worried since i could have touched vaginal fluids if i put on the wrong side. Please help.
    For scenario 3, I think I used the condom right because I checked it after and saw semen inside. Also tried to push them out but the condom is intact. So is it safe to say its OK?

    • drtan

      1. No. 2. Condoms are not 100% protective. You are at risk but not because you touched the vaginal fluids. 3. No. Please read: http://www.drtanandpartners.com/how-effective-are-condoms-diaphragms-and-circumcision-in-preventing-hiv-transmission/#.U40fFLr2MeE

      • worriedsick123

        Dear Dr Tan,

        From the link, I understand that I am at risk for No. 2 because I didn’t check if he condom was intact? Whereas for No. 3 I checked so I didn’t have a risk? Is the assumption correct? (For the record, the condom I used was latex: does it make a difference?) I am a bit confused as to a difference in your answer to No. 2 and 3. Can you please calrify? For No. 2, my worry was that my penis might have touched the vaginal fluids which could have gone inside the urethra when I resumed having sex after putting on a new condom.

        Regardless, I did take PEP after 17 hours of possible exposure (DuovirN – for two days) and then switched to Duovir for another 28 days. I couldn’t get top of the line PEP as I am in a third world country. So, now I am worried about the efficacy of the generic PEP. Can you shed some light on it?

        I had a P24 Ag/Ab test 18 days after possible exposure and another one at 33 days after exposure. While taking meds, I had a sore throat on 16 days and fever of 100.5°F as well as bad taste in mouth and night sweats. Also currently 34 days after, I am having another sore throat, cough and sneezing, no fever though. Could these be due to ARS? Can you help?

        • worriedsick123

          Dear Dr. Tan,

          I meant to say I had two combo tests at 18 and 33 days after possible exposure and received nonreactive for both tests. Can you please just clarify on my first paragraph though if you don’t want to discuss symptoms (since they are not reliable anyways.)

          I have been very anxious and depressed Dr. Tan. Every single day all I can think about is this issue of possibly having contracted HIV. Sigh.

  61. Hiv antigen and antbodies after 28 days but while on prep.
    Dear doctor,does pep alter the results of antibody and antigen test done during the last day of pep(it was dose 29 out of the 30 indicated)?

    • There is a theoretical possibility but honestly I do not think the PEP affects the tests at all.

  62. Lar (Male)

    Dear Dr,

    I have been having a hard time for the past couple of weeks due to one particular incident. I know I did something very wrong and suffering from the outcome. It is really difficult.

    On 3rd of May (Friday) I had an encounter with a Filipino trans sexual sex worker in SG.There was absolutely no penetration involved , but I received oral sex from this person with a condom on and it was intact (condom had a reservoir tip , I hope this is a non animal skin condom :( ). The only other act was I sucked this SW breast but it was not a serious sucking , more like I was licking her nipples.

    Having done this I got freaked out and I ran to a doctor next day and insisted on PEP. Doctor did not prescribe but I really insisted so he gave me 28 days PEP (Combivir and Kaletra) and I completed this.

    After the completion I had a rapid anonymous (Ag/Ab combo test , 4th Gen) test at your place after completion of pep (38 days from the exposure ,9 days after PEP ). The result came negative and the lady doctor said this is 99% accurate.

    I am very afraid to go back to the doctor who prescribed me PEP because if I find positive I do not know what I should do being a foreigner here

    could you please help me get out of this misery , I am unable to focus due to this constant fear of hiv. I tend to check my self every now and then to see symptoms and I am going crazy now!

    1. Doctor do you think I was at risk ?
    2. The test I did after PEP , is it conclusive ?
    3. Do I need to test again after 3 months post exposure ?
    4. What would be the chance that this result may change in 3 months?
    5. Do animal skin condoms have reservoir tips similar to latext ?

    Doctor please please help me!


    • Dear Lar,
      You’re worrying yourself too much.
      1. Your risk in the first place was negligible. By CDC standards, receiving oral intercourse with a latex/polyurethane condom on is a zero risk event of getting HIV. Even receiving unprotected oral sex is considered a very low risk event.
      2. Yes, your test is conclusive.
      3. You can retest if you want to, but I don’t think there is a need.
      4. In your case, nil.
      5. Reservoir tips are a design feature specific to the manufacturer and make of the condom rather than the materials used as far as I know.

      • Lar (Male)

        Thank you doctor , It was a very relaxing statement and I hope you understand how much it means. I would never ever ever again do this kind of foul act certainly. The agony was too much and I really could not put that into words. Much kudos to you and your team.

  63. Johny

    Dear Doctor, I have an anal sex with a unknown hiv status person after 14 hours i take twice a day kaletra and once a day truvada.I have completed pep for 30 days and i have two hiv tests,the first test take it after completion of the pep (30 days after exposure or next day after pep) also the second test i do it in 3 weeks after pep or 7 weeks after exposure(all tests are negative).i have some questions about tests. How accurate are the last test i take and also i need to repeat test a 3 monts

    • drtan

      Very accurate but not conclusive. Yes you need to repeat the test at 3 months.

  64. Hello Doctor Tan,

    I found your website while I Google. It is very useful and extremely helpful.

    I was on PEP on day 3, and almost 70 hours late. My testing are all negative:

    – Week 6, ab test
    – Week 9, ab/ag Combo Test
    – Week 10, ab test for Hep B and Hep C
    – Week 12, ab/ag Combo Test

    Again, all these tests are Negative.

    Due to location matter, I did not get to follow up with my PEP doctor. The last thing I remembered is he said 3 months test is enough.

    I’ve been having many ARS look-like symptoms and I still feel anxiety suffering from having watery stool every morning soon after my coffee.

    Because I did not get to follow up with my PEP doctor. I would like to apologizingly ask few questions:

    1. Does the morning watery stool after coffee look serious? Honestly I’m not sure if it’s due to Stress… I can’t control my feeling recently.

    2. Do the different PEP drugs make different window periods?

    3. You mentioned many times above that 12 weeks or 3 months are conclusive. So does this also count in my case?

  65. Chucks

    Hello Dr. Your good works obviously stands out.
    Please i need your honest opinion. I know 3 months test is conclusive based on official guidelines However have you ever seen 8 weeks negative antibody test ( 4 weeks post PEP) change. How conclusive can I believe this will be based on your experience.


  66. Dear Doctor Tan,
    I send you a comment in july 6 2014 and i want to inform you about my new test i have after 2 months of my exposure with 4th generation ab/ag test which is negative.
    My first question is the last test conclusive?
    Also i read from this site http://i-base.info/ that someone who have test one month post pep is 95% accurate with 4th generation test and if someone wants 100% result must wait 3 months after finishing PEP.
    Thank you.

    • According to new guidelines, patients post PEP must test up to 3 months to be 100% accurate.

  67. Lorenso

    Hi Dr Tan,
    After taking PEP for 28 days some say to get a conclusive result one has to test after 3 months from the date of exposure. Does this mean that from the date that the exposure happened or from the date that last dose of PEP is taken. Please help to understand this. I am thinking of doing a quick combo test at your place , but need to get these dates correctly understood. Thanks Thanks! Lorenso

  68. Dear Dr. Tan,
    Apologies for the long post.
    I am one of the many people who have approached you for a counsel in Sept 2013. I would please like to share my experience.
    My exposure was a condom burst incident with a CSW, I was on PEP at the 21st hour after exposure. I had a positive qualitative RNA PCR from a blood draw taken on the 12th day. My doctor had advised me that this indicates an infection and that I should stop PEP, all my research indicated that the PEP should be taken for 28 days so I continued against the doctors advice.
    I had a second blood draw on the 16th day which was undetectable. I was very apprehensive at this point and didn’t know who to approach for advice. Seven weeks after PEP I had a fourth generation Ag/Ab test which was non reactive. The information available on the Internet was contradictory and to top this I work in a middle eastern country with archaic laws on HIV tests.
    It was at this point that I approached Dr. Tan for his advice, he advised me that I did not have to worry since I had a non reactive test at the seventh week after exposure, no one else was able to give me an assurance or hope except Dr. Tan, To top this I had an case of urticarial rash and a a fever for 3 days at seven and eleven weeks after exposure respectively.
    The problem was that I work in a middle eastern country with archaic laws on HIV testing and could only take leave in July 2014 which was 11 months after exposure. For the last ten months, I used this page every single day must have been here a million times and this was the only thing that used to calm me down. Today (eleven months after exposure) I had a fourth gen Ag/ Ab test which was non reactive, thank god.
    Dr. Tan I cant thank you enough, you were the only person who had given me hope. I have immense respect for your selfless work. I wish you the very best in life, I would be delighted if I can make an humble contribution to your noble cause.
    As for me I have learnt my lesson, this was the first time that I had visited a CSW and never again, It was a harrowing experience.
    Thank you very much Sir.

    • I am very happy you are well and am equally happy we could offer some help to you during our ordeal. Thank you very much for sharing your story. That is all the contribution we need.

  69. Dear Dr. Tan,

    4 days ago, I had a sex with guy working in massage shop ( I just have strong feeling that the guy is NOT clean – might HIV+) I we hand protected anal sex then I sucked him unti he cum in my month. Sorry for being descriptive this way.

    My questions:

    Is my sexual contact considered high risk exposure?

    Do I still have a chance to start PEP? After more than 72 hours

    I would really appreciate you prompt response

    Best regards

    • Yes. Absolutely. Anal sex is the highest risk sex act. There is no point starting PEP after 72 hours.

  70. Worries123

    Hello Dr.Tan,

    I know you’re always keep up to date of current researchs. If a Combo Test on week 12 from exposure is Negative… Base on your knowledges and expertist, do you recommend re-test?

    If you do recommend re-rest? What is the reason?

  71. Januário

    Hello Docs,

    I work as paramedic in ambulance at peru, almost one year ago i hurt myself when i help a pacient, he was hiv positive.

    I’ve iniciate PEP 2 hours after for 28 days, and done the following tests

    1) 4 weeks post exposure Duo Test-Negative
    2) 8 weeks post exposure Duo Test-Negative
    3) 12 weeks post exposure Duo Test- Negative
    4) 16 weeks post exposure Duo Test- Negative
    5) 20 weeks Post exposure Duo Test -Negative
    6) 26 weeks (180 days) Post exposure Duo Test Negative

    Per law and insurance, i have to take one more test at one year, i want to know doctors, if you have seen at your clinic, someone change result between six months and one year. Thank you!

    PS, sorry for my bad english, i never study, learn it at movies ;)

    • My friend your English is superb. Thank you Hollywood. I am utterly convinced that you do not have HIV. I think your tests are more than enough to be conclusive. Please do not worry about your test at 1 year. I am sure you will be fine. You inspired me to read up on Peru. It is a most beautiful country.

      • Worries123

        Dr. Tan,

        I think Januário is so brave to take the test monthly. No many can do that… I wish him good luck and good health.

      • Januário

        Thank you Doc, i hope to know Singapore one day, it’s a fantastic country!

  72. Dear Dr Tan and Partners

    Firstly thank you for the very informative site and blog, it’s greatly appreciated. I have read all the posts above and the respective comments and your responses too which are quest informative to the uninformed.

    I have also noted that no cases above are similar. I myself have been exposed as follows:-

    I had varginal sexual intercourse on 05-06-2014 which started of with lots of foreplay with my female sexual partner releasing varginal fluids which I touched with both my hands and male organ and then without drying used the same hands with sexual fluids to wear the condom. I was the insertive partner with her being on top the intercourse lasted a few minutes approx 5 minutes. On completion I noted that she had released an abundance of sexual fluids which I wiped and discarded the condom.

    24 hours after the incident we confirmed she was positive and I negative via rapid tests. At the same time I was started on a Pep regimen of Lamivud/Zidov and Lopinavir/Ritonavir on 06-06-2014. I reacted terribly to the combination with diahoreah and the regimen was changed on 07-06-2014 to Truvada and Instress for 30 days and a single once of dose of Zithromax. All base line tests done were negative. On 27-06-2014 I developed a sore throat,29-06-2014 excessive sweating at night, on 02-07-2014 developed a genital pimple on my inner thigh which dried the following day, was tested 6 weeks on 14-07-2014 hiv 1/2 rapid negative and hiv 1/2(4th gen)-negative I am hove ever experiencing joint and muscle pain and lower abdominal painon and off during and after pep treatmentto date, I have also had a flu infection sore throat with white sputum and mucus that hasn’t responded well to flu medicine and amoxylin antibiotic for three weeks now.

    My questions are 1) could I have been exposed indirectly by the sexual fluids on the organ and hands when I wore the condom 2) could I have delayed sero conversion sickness due to the muscle ,joint and abdominal pains 3) what are the chances of the next test results on 04-09-2014 changing to positive thus far

    Your usual help and assistance will be greatly appreciated as I’m confused and lost

    Looking forward to your favourable response



    • 1. I don’t think that is a relevant question. I think you are at risk simply because I know condoms are not 100% effective. That said, I think your risk is extremely low. 2. You are assuming your symptoms are due to HIV seroconversion. I do not think this is the case. 3. No chance. You are OK. Don’t worry.

      • Dear Dr Tan

        Msny thanks for the response it’s highly appreciated and acknowledged. I have however also discovered lumps on both my upper rib cages both the left and right, and these are painful when touched these are situated way below the armpits but before the end of the of the ribs, could this be an hiv related symptom.

        Lastly after how many weeks is an rapid hiv test conclusive in the absence of elisa test

        Thank you once more


        Thandi T

        • Again your question on symptoms is not relevant. I honestly think your tests are already accurate. However, because you took PEP, officially you must test till 3 months post exposure.

  73. Dear Dr. Tan.
    Greetings from India,
    First of all i would like to thank you for the wonderful work you are doing and i would like to apologize for my bad English.
    I would really appreciate if you can help me 6 weeks ago i had a low risk exposure fingering a sex worker in Mumbai i had a small fresh cut on my finger i insisted on the doctor to give me Pep i started it 65 hrs after exposure.
    -20 days after exposure i did a DNA PCR qualitative test the result was: Not detectable , my doctor said it was conclusive and to stop Pep but reading online i realized that while on Pep we can have a false negative especially that i had a sore throat for almost 4 weeks after exposure
    – 39 days after exposure , 10 days after finishing Pep i did an Elisa test (4th generation) also the result was : Not detected .
    Should i do further Testing ?
    6 weeks now after exposure i still have ulcers on my tongue , joint,muscle and stomach pain is it HIV early symptoms or Side effects after stopping Pep ?
    Thank you

    • You were not even at risk of HIV in the first place. I do not see a reason for you to worry.

  74. I have found this update from US CDC. It is said the follow up testing may be concluded at 4 months if 4th generation test is used.


    I have got my HIV test from week 16 via E.C.L.I.A ab/ag. And it is negative.

    However, I have concern regarding to my Complete Blood Count. It showed that my WBC is 6900 and lymphocyte percentage 19.2% with absolute count of 1325, which is lower than the normal range (1500 – 4000) from the lab.

    Another concern is that I was a bit over 67 hours late for PEP, but still within 72 hours. My baseline CBC showed that my WBC is 8650 and lymphocyte percentage 12.4% with absolute count of 10735, which is lot lower than normal range (1500 – 4000) from the lab. My Neutrophil is normal on week 16. All other number in CBC are good.

    My HCV and HBV test via E.C.L.I.A at week 16 is Negative. I did not take any drugs or having any cold. My Neutrophil is 78% (a lot higher than normal range). All other number in CBC are good at baseline.

    Few questions I want to ask from your expertise.

    1. Does the CBC test at my baseline of PEP hint anything serious issue?

    2. Dr.Tan, Normally do you perform CBC for your PEP patient? If yes, did CBC hint anything to HIV infection? (taken my CBC number as example)

    3. That’s an updated poster from US CDC updating said 4 months is enough for following up if 4th generation test is used. My week 6 test was normal ab test. I only got the 4th generation test three times on week 9, week 12, and week 16. You said in your forum that p24 drop after 6 week. So I worry that the US CDC mention that 4 months is enough, but this does not count in my case… as I only did 4th generation test after 6 week. Do you think I need to retest at 6 months mark?

    Thank you for your answer.
    I hope my worry is only just worry…

    • 1. No. 2. Yes. No. 3. I think your 4th Gen test at 6 weeks is already conclusive. However, officially I test up to 3 months. How long you should follow up for depends on your doctor. Please ask him on your next follow up.

      • Thank you Dr.Tan,

        Actually my week 6 test is only ab test. The combo test are on week 9, week 12, and week 12.

        My doctor said 3 months. But due to many information on internet and different guidelines from many countries… make me worry and confusing.

  75. Dr. Tan- I had unprotected insertive anal intercourse with a stranger whose status I don’t know. It was four quick strokes- I pulled out and went to a clinic for PEP. Given the low risk of the exposure (USA), they only gave me Truvada.

    I finished the Truvada with 100 percent adherence.

    My tests so far:
    – At Day 25 still on PEP I had a rapid test that was negative.
    – 4 days after completing PEP, 4.5 weeks after PEP, I had a DUO test that was negative.
    – 12 days after completing PEP, 6 weeks post exposure- I had a rapid test that was negative.

    I know I need to test out until 3 months, but are my results indicative? I’ve been worried about ARS. I haven’t had a fever or rash, but have had some sinus and headache and phlegm issues the past few days. If I was seroconverting wouldn’t I have antibodies to make my rapid HIV test positive? Or can I attribute my feeling down to the 5 international flights I’ve taken in the last 4 weeks coupled with PEP stress?

    Thank you so much for your work.

    • I should also include I began my Truvada as PEP 8 hours after my exposure and I’m a gay male who briefly penetrated another gay male in the US. Just convinced my minor headache and cough is seroconversion – though I took a rapid test an hour ago and it was negative and I’ve been feeling this way for 3 days!

      • Chill it man. You do not have HIV. Your tests are already super accurate. Stop over-interpreting your symptoms. The more you think about it the more symptoms you will have.

  76. Dear Dr Tan

    Further to the above sore throat and flu I visited the local clinic where I was asked to take a PCR DNA test which I was advised is more conclusive than the 4th generation test. My question is then 1) is the pcr more effective given that my tests to 6 weeks after exposure have been negative on 4th generation test and rapid tests.

    Thank you




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