Dr. Tan and Partners is one of the few approved Anonymous HIV Testing Centres in Singapore. A detailed write up on our service is available here.

Other STD services: Early STD Screening, Rapid Hepatitis B Blood Test, Swab for Gonorrhea and many more... contact us to make an appointment now!

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.

Click here for HIV Testing FAQ

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.

Early, Fast and Accurate Anonymous HIV test – Click Here


 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.

HIV Signs and Symptoms

If you have any questions, visit our free online forum on sexual health, HIV and STDs.

Click here for Info on STD Symptoms in Men
Click here for Info on STD Symptoms in Women
Click here for Info on HPV Testing in Men
Click here to see the full range of our HIV/STD Services




Need more advice?

Come down to Our Clinics for a discussion with Our Doctors, or call our clinics for more information:

1.) Robertson Walk (Anonymous HIV Clinic)  (+65 6238 7810)

2.) Bencoolen Street (+65 6884 4119)

3.) Novena Medical Centre (+65 6397 2095)

4.) Raffles Place – PLUS (+65 6962 7144)

5.) Somerset – Orchard Building (+65 6262 0762)


Click here to see the full range of our HIV/STD Services


Where to find us – here

Selected clinics are open on Saturday and Sunday.

Email: hello@dtapclinic.com

All Our Doctors are Fully Certified and Trained to conduct specialised STD Screening,  STD Testing & STD Treatment and HIV Testing.

For lady patients who prefer female doctors, we have professional certified female Doctors to attend to your medical needs.


Feel free to email your queries, feedback and suggestions on what other topics you want to see in the comments section below.


Click here for PEP details including prices.

More on HIV symptoms.

If you have any questions, visit our free online forum on sexual health, HIV and STDs.

If you need a HIV test visit Our Clinics anytime during our opening hours. You do not need an appointment.

Find out more about Anonymous HIV testing at our clinics.

Can’t wait for 3 months to find out? Find out more about Anonymous Rapid HIV Combo test at our clinics.


If you had a high risk exposure to HIV within the past 72 hours, you can take medicines to reduce your risk of actually contracting HIV. Find out more on HIV PEP Treatment.

Click Here for Contact Details, Address and Opening Times.


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.

Find the profiles of our panel of doctors.

All prices quoted below excludes prevailing GST


Consultation STD Consultation – $60.00

Anonymous HIV Rapid Test only $20.00
(not inclusive of test)

STD screening
Standard HIV, Syphilis, Hepatitis B/C, Herpes Simplex Virus Type I and II $ 200.00
Urine – Chlamydia and Gonorrhoea PCR, Monilia, Trichomonas, NSU, Mycoplasma, Ureaplasma, Urine Culture, Candida $ 280.00
Urethritis and Vaginitis
Vaginal Swab – Chlamydia and Gonorrhoea PCR, Monilia, Trichomonas PCR, Gardnerella PCR, Candida PCR, Group B StrepNSU, Mycoplasma, Ureaplasma, Direct Microscopy, Candida, Vaginal swab culture $ 345.00
Comprehensive (Male) Blood – Syphilis, Hepatitis B/C, Herpes Simplex Virus Type I and IIUrine – Chlamydia and Gonorrhoea PCR, Monilia, Trichomonas, NSU, Mycoplasma, Ureaplasma, Urine Culture, Candida $ 390.00
Comprehensive (Female) Blood – Syphilis, Hepatitis B/C, Herpes Simplex Virus Type I and IIVaginal Swab – Chlamydia and Gonorrhoea PCR, Monilia, Trichomonas PCR, Gardnerella PCR, Candida PCR, Group B StrepNSU, Mycoplasma, Ureaplasma, Direct Microscopy, Candida, Vaginal swab culture $ 525.00
Individual STD Tests
Determine Syphilis test Rapid Syphilis Test $ 50.00
Determine Hepatitis B Test Rapid Hepatitis B Test $ 50.00
Herpes Simplex Virus PCR Herpes Simplex Virus Polymerase Chain Reaction (PCR) Test $ 200.00
Chlamydia and Gonoccocal PCR Chlamydia and Gonorrhea
Herpes Simplex Virus Type I IgG Antibody Herpes Type 1 $ 40.00
Herpes Simplex Virus Type II IgG Antibody Herpes Type 2 $ 40.00
Non-Specific Urethritis (NSU) Culture Mycoplasma, Ureaplasma $ 118.00
HIV test
HIV RNA/DNA Polymerase Chain Reaction (PCR) Test $600
Add $100 for expedited results
Rapid Fingerprick Blood HIV-1/2 P24 Antigen/Antibody Combo (HIV Duo Test) (4th generation!) $ 150.00
Rapid Oral Saliva HIV-1/2 Antibody Test (Oraquick) $ 50.00
Rapid Fingerprick Blood HIV-1/2 Antibody Test (Determine) $ 50.00
PEP $2000 – $2200


  1. Hello Doctor
    I had protected vaginal sex with a woman working at a massage parlour in Thailand
    I am not too sure whether or not the condom broke as I was quite drunk and it was dark
    However, I visited the local clinic next day and requested to be put on Truvada as PEP
    I tested negative on the combo test 53 days after exposure
    What are my chances of being infected because I have read some stories about PEP delaying seroconversion
    Thank you

    • I do not think you have been infected based on your test result. If you are still worried, you can get a HIV antibody test 3 months from exposure.

      • Hi Doctor
        I just got my negative duo result 2 months post PEP (3 months post exposure)
        Can I take it easy now?
        Thank you

        • In my opinion your test is conclusive. Although in some countries the recommendation is still to retest at 6 months post exposure for patients who have been on PEP. It also depends on what test you have done. Please verify this with the doctor who prescribed you the PEP.

  2. WorriedSouthAfrican

    Hi Dr. Tan/Sii & Sim

    I’m not sure if my last comment was posted correctly on your site as the connections here in South Africa are not too good and Inhave posted previously where there was a response however the last posts did not receive a response.
    I am so sorry if this is an excessive post, I do apologize in advance – I do not mean to rash you.

    My scenario: I had a protected sex with a CSW here in Johannesburg, South Africa almost 6 weeks ago however during the intercourse the condom broke, I ejaculated and only realized after I pulled out. I had a very minor penile abrasion at the time as well, there was no visible blood but there was certainly a skin break which was visible. The CSW told me she was HIV negative however just wanted me to leave when I asked her, so this did not give me a wholeness of comfort especially given the fact that HIV is prevalent here in South Africa, especially in my city, Johannesburg. I contacted a doctor in the city that morning and I took Trivenz (Atripla generic) PEP 7 hours after the incident and was adherent to it for the 30 days without missing any doses. I must make mention that I did have a few drinks whilst on the PEP however did not abuse alcohol during this time. On day 10 post exposure, I took a DNA PCR test and a full STD panel of tests. Everything was negative.
    Since the completion of PEP I have taken the following tests:

    Day 10: DNA PCR – Negative
    Day 16: Duo/Combo & PCR – Negative
    Day 28: Rapid (Core brand) – Negative
    Day 32: Duo/Combo – Negative
    Day 36: Rapid (Core brand) – Negative

    I have the following questions for you (these questions answers will be viewed as your opinions and not medical advice as I realize that you cannot give out such). Please could you assist me with answering them – I will try keep it as short and to the point as possible:

    1) I am aware that I would need to test again at the three month mark however have you seen/experienced a patient/s who have turned positive after a negative Duo Test upon completing well adhered PEP (Day 32 post exposure). Plus the addition of a negative Rapid Test at week 5 (Day 36 post exposure) turn positive afterwards?

    2) I am going back to the lab during this week for the 6 week HIV tests which are the Duo Test & PCR Test; this would be 6 weeks post exposure but 2 weeks post PEP completion. If both tests are negative, would you deem the result conclusive?

    3) I had a full STD screen 10 days post exposure; all results were negative. Could the tests have missed any STD and if so which ones (given their window periods)?

    4) I read quite extensively that if there is a co-infection of Hepatitis C, this further extends the window period for HIV testing. Is this true?

    5) I have read that it is not really common for Hepatitis C to be transmitted sexually as its blood borne unless there is blood contact during that sexual exposure.
    a) Is this true?
    b) What is the likely hood/statistics for such transmission given my scenario of the broken condom with ejaculation and the penile abrasion? (If it is possible to answer this at all).

    Please answer these questions. I am going through the worst 6 weeks of my life. I will never make this mistake again, it’s definitely changed me forever and I am praying everyday that I have not contracted a lifelong virus from the stupidity of my actions. I am sure you hear this all the time but I am in a place of darkness and ask these questions via your forum as a beacon of hope for honesty and best professional opinion even though you are all across the globe.

    Thank you for your kind work and reply.


  3. Hi. Firstly, this is an excellent forum and I think that the advice (which I appreciate isn’t medical) you provide is comforting to many, or at least prompts those at risk to seek medical advice. My situation is as follows: Mostly protected (torn condom) with CSW in Sub Saharan Africa of unknown status but from a high prevalence population. Prescribed PEP at 60 hours. Of note, the regime was dated in that it contained Nevirapine but that is all that was available and I accepted the associated risk. Tested at baseline: Negative; and at day 28 of PEP: Negative. This was fine in sub Saharan Africa and I can only assume that these were early generation tests. All I got from the Dr was that they would test for Antigens and that this would not be affected by PEP. I took a subsequent duo test at a different location at 11 days post PEP and 6 weeks after exposure (as per WHO guidelines) which came back negative. I understand that you have never seen a duo test after PEP change to positive at a later date but would be extremely grateful if you could answer the following questions. 1: Is that statement true for tests taken at the six week post exposure interval? 2: Is this at least some evidence that PEP does not stop P24 antigen production? 3: If not, why are duo tests reliable after PEP (i.e. All post PEP tests would be negative would they not? 4: I intend to retest at the 3 month mark (post exposure) with a duo – is that advisable / conclusive? Many thanks in advance. It is genuinely appreciated. J

    • drtan

      Thank you for a very well written post. 1. Yes it is. You Duo test at 6 weeks post exposure is really as good as conclusive. 2. No. But there is no evidence that PEP stop the production of P24 antigens either. 3. There is no evidence that PEP affects HIV test accuracy. 4. Yes it is advisable and will be conclusive.

      • Dr Tan, thank you for your conceise reply, I am truly very grateful.

        • WorriedSouthAfrican

          Hi J

          Could you help answer some questions? Your reply will be with gratitude.

          1. Which Sub Saharan country was it?
          2. What regimen where you on?
          3. Did you have any “symptoms” at all during the 6 weeks (like anything at all)? I ask as I had some minor symptoms during my 6 weeks, it’s currently heading up to 6 weeks now. I tested negative with these tests:

          Day 10: DNA PCR – Negative
          Day 16: Duo/Combo – Negative
          Day 16: PCR – Negative
          Day 28: Rapid – Negative
          Day 32: Duo/Combo – Negative
          Day 34: Rapid – Negative
          Day 35: Rapid – Negative
          Day 36: Rapid – Negative
          Day 37: Rapid – Negative
          Day 38: Rapid – Negative

          I have a slight sore throat at the moment though nothing too bad but I am worried (obvious judging from my posting name).

          I am going to have a 6 weeks test done in day 42 in a few days.
          Wish me luck! I need it for this stress and anxiety.

          Thanks in advance for your reply.

          • Hi, it’s was Nigeria and I was proscribed nevirapine lamivudine and zidovudine which isn’t advised for PEP due to adverse side effects. I felt a little sick but put that down to the PEP. I also had a rash on my arm at around week 4) which again could have been PEP related (I think?) and currently have a mild sore throat also, but nothing serious. Good luck with your test – I’m not a Dr but from the research I’ve done I’m confident you will be fine. J

  4. Slept with a HIV lady on the 17th of December 2015 and was given Pep 4 days after my exposure which I took for 7 days but stopped because of the side effects. Have tested countless time since January and the last test I did was on 7th June which all came negative. Please I need to know if my result is conclusive. Thanks

  5. WorriedSouthAfrican

    Hi Dr. Tan & Partners

    It’s the WorriedSouthAfrican from Johannesburg – after all your feedback (I wouldn’t say advice as I am aware of how you are quite stringent on medical advice).

    As explained previously, I had an incident which warranted the initiation of PEP which I have successfully completed without missing a single dose. Initially I took a DNA PCR test at 9 & 26 days, both of which were negative. Today, being 32 days post exposure I took a Duo Test – the result was negative. I have a few questions on your opinion:

    1) I am aware that I would need to test again at the three month mark however have you seen/experienced an patients whom have turned positive after a negative Duo Test upon completing PEP? (Duo Test taken immediately/2-3 after completion of well adhered PEP which was negative then later turned positive)?

    2) I am going back to the lab next week for the 6 week test (Duo Test) – if this is negative would you deem it as pretty much conclusive? It would be 6 weeks post exposure but 2 weeks post PEP completion?

    3) Would you recommend a DNA PCR test at this point as well? Just to be sure? This would be T 6 weeks post exposure and 2 weeks post PEP completion?

    4) have muscle pain/aches in my shoulder blade, would this be a part of seroconversion? It is an unusual aching that I have never experienced previously.

    5) I had a full STD screen 9 days post exposure – all results were negative. Would I need to retest for any of these STD now at Day 32?

    6) If you answered yes for point 3, which STD have a delayed response to tests that I should test again for?

    Please note I won’t take your feedback as medical advice but just your opinion from your experience in this field as I am aware on your medical advice stance and do fully understand and respect it.

    Thank you doctors. Your forums are the beacon of hope and comfort for people like me, people from he around the world! We salute you!!

    • WorriedSouthAfrican

      *Apologies the first PCR’s were completed at day 9 & 16, not day 26 (this was a typing error)

      • WorriedSouthAfrican

        Hi Doctors

        Here is a more detailed update on the tests (post exposure via vaginal intercourse following a condom break with ejaculation and small penile lesion, I am male and the CSW was female):

        Day 10: DNA PCR – Negative
        Day 16: Duo/Combo & PCR – Negative
        Day 28: Rapid (Core) – Negative
        Day 32: Duo/Combo – Negative
        Day 35: Rapid (Core) – Negative
        Day 36: Rapid (Core) – Negative

        I am going to test again at Day 42 (6 Weeks) using both the Duo/Combo & PCR test however subsequent to the questions above, what do you make of these results?

        7) In your opinion what is the likely hood that it will change to positive if any?
        8) Relates to question 1) have you seen this trend of testing ever turn positive in the end?

        Eagerly wait upon your respond.

        Thank you!!

  6. on PEP

    HI Doctor, I am on PEP and it has been 26 days post exposure. I took a combo test on Day 26 which is negative. How indicative is this?

    • Very indicative.

      • on PEP

        Thank you Dr Tan. I took the combo test on Day 28 and Day 29 post exposure which both are negative. I still have last 2 days of PEP for a full 30 day course. Shall i test again on completion of the PEP?

        • In my view you should test within 2 weeks of completing PEP and again at 3 months. Please verify this with the doctor who prescribed you the PEP.

          • On Pep

            Thank you Doctor , I tested negative with combo test on day 35 now post exposure. How indicative is that ?

          • On Pep

            But you have not seen anyone from pep at 4 weeks post exposure turn from negative to positive at 3 months post exposure right?

  7. Dr, I was exposed to a lady who is co-infected with HIV & HCV, the condom broke and 18hours after exposure, i was placed on PEP(tenovofir,lamivudine, efavirenz), 25weeks after pep my HIV antigen & antibody test is Negative, same with my HCV antibody test, is it conclusive?

  8. Condom break case.Exposure date 18 Jan 2016 . Had pep under 40hrs.Got myself retest after 3 months after exposure – negative.
    lady test that work in spa – 22 Jan 2016 ( combo test ) & again 20 Feb 2016 ( combo test & pcr dna test ) all negative .
    1) pep effect window period ? 2) should I ttake 6month test? 3) any help and guidance you provide will be helpful.

    • You do not have HIV. Your tests are conclusive. You do not need any more tests. Forget about it.

  9. mikael fata

    g morning sir, apr 1 had an unfortunate surprise with a massage therapist, he entered me without a condom, as he was extremely small did not realize for about ten seconds what was going on. 2 days later i was on pep, truvada and isentress. they did rapid test and 4 th generation hiv ag/ab w/rfl test. negative . 5 days after finishing pep they did a rapid test and again the 4 generation hiv test, negative again, dr said that i was in the clear, is this true?

    • Yes, since your test was negative. If you are concerned, you can get yourself tested again 3 months from exposure.

      • Mikael

        So went and got a rapid antibody test but it’s 10 weeks post prep but 15 weeks post exposure , and of course I had a 4th gen duo test 5 days after finishing pep all negative, can I put this to rest or do I need to do another test at 12 weeks. Thank you .

  10. Sir I bathed my brother who is hiv positive he was on his last stage I did p24 antibody and antigen test 4weekss and 2days after exposure. At pathcare med diag. it came out negative. I have a serious cough. Headache and sore throat and allthe symptms.rashies on my neck. I was told I have typhiod.pls I did alere antibody rapid finger prick it came out negative. M depressed and my husband is not happy but my mood.am based in nigeria.plss reply

    • You cannot get HIV by bathing a HIV positive person. Your symptoms are not related to HIV. See a doctor and get yourself assessed properly.

    • Actually I had a hangnail on my hand when cleaning his body that’s my fear

  11. Hi sir I’m HIV pcr DNA qualitative test oftr 28 days and common HIV test 4,6,8 months nd 9mnth repeat also pcr DNA qualitative test and 12 month,23 mnth common HIV test .all tests come out negative ..but i have urine infection sir it tests all conclusive r not sir ..plz reply

  12. Revan

    Dr. Tan/Dr. Liong,

    I’d first like to say that what you’re doing here is godsend (religion aside). I’m sure that I speak for not just myself when I say that your feedback, insight and advice is valuable, impactful and incredibly appreciated.

    After a low risk HIV sexual assault exposure (vaginal intercourse with person of unknown status), I started PEP. Tonight is my 2nd night taking Truvada & Isentress. When I visited the ER, blood work was performed; an antigen and antibody combination test. The physician on staff informed me that the HIV antigen blood test given would provide very accurate HIV results within 72-96 hours. He mentioned that this is the same exam that they provide nurses if they are exposed in the workplace. This goes against a lot of testing guidelines and literature out there. Percentage wise, how conclusive is an HIV antigen exam after 96 hours (4 days)? Would Truvada & Isentress affect the antibody/antigen results at all?

    Thank you once again. Your time and medical opinions are truly appreciated.

    • drtan

      I honestly do not know why the physician would have told you that. I think there must have been some sort of miscommunication. The first 10 days after a HIV infection is known as the eclipse period. During this time NO TEST IS ACCURATE.

  13. Dear Doc Tan, l foolishly had unprotected vaginal sex with a female and started PEP 36 hours later. l had a mild sore throat about 4 days later and 3 weeks later l had a rash on penis which lasted 3 days and disappeared after l applied antibacterial cream. l panicked nd went for hiv test using 4th generation CMIA. lt was 231/2 days Post exposure.lt came out -ve. How encouraging is this?

    • Very encouraging. However, you should still repeat the test at 3 months. Also, screen for other STDs and see a doctor about that rash on your penis. If you wish to see us, you can CLICK HERE for location info.

      • Im currently on pep (truveda and isentress).. it has been 11 days past the exposure.. i understand the window period (antibody testing) for pep is 3 and 6 months after taking pep.. would the rna/dna testing be accurate?

        • drtan

          There is no straightforward answer. Please ask the doctor who prescribed you the PEP.

    • The machine used is for screening blood at blood bank and also did syphilis,HBS and HCV which all came out -ve. Can l do one 6 weeks after exposure. How conclusive will that be? Difficult to wait 3 months.black am a bag of nerves and suffering from panic attacks at times. not a healthy situation.

      • Hello Doc. l asked if a test at 6 weeks or 8 weeks post exposure would be helpful. 3 months is wait is very stressfull. How close is the 24 day test l did compared to 28days? Would the 4 day difference affect the result that much?

        • Chama

          Hello Doc, I did a 4th Generation CMIA test 7 weeks post exposure with is 3 weeks post PEP. It came out -ve. Is this as gud as conclusive?

          • Chama

            Hello Doc, l did a PCR test 28days post PEP and it has come out -ve. Can l move on now?

  14. Precious

    hello doctor, I was exposed to an HIV positive patient on 27th November 2015 and was places on PEP (tenofovir, lamuvudine, efavirenz) 17hours after exposure, its now 16weeks post pep & 20weeks post exposure, my test via 4th generation test is negative, is it conclusive?

    • In my opinion it is. Please verify this with your doctor.

  15. Adamu, A.Y

    A brief update sir.
    All test taken were rapid standalone antibodies test. Alere determine, statpak, unigold, healgen, Advanced Quality, star gold ultra, double check were used.
    thank you.

  16. Adamu, A.Y

    Good day Doctor.
    Hoping you will help me.
    I had a blood exposure on 23rd November 2014. (bloody brawl) a couple of weeks later, I fell sick and took the usual tests for malaria and widal and were both positive. I had a full course of medication and got cured.
    however around 68 days post exposure, not feeling well, I decided to run a full blood test for Hep A, B and C, Vdrl, and HIV. all were negative. It was then I told the Doctor about my exposure, the social status of my fight mate and my subsequent illness. He said if I had visited him earlier, he would’ve prescribed PEP for me. He outlined the supposed efficacy of PEP. I become worried and suspects I’ve been infected with HIV. I insisted and was put on 28 days course of pep.
    I took all these tests again 10 days through PEP and a week after its full course all negative.
    from 2014 to date 29th March 2016, I had ran approximately 50 blood test and all are negative.
    I still do not feel fine. no fever. just lymphadenophaty under arms, groin, neck and head plus a faint earache.
    my specific questions are:
    1. can I rule out Hep A, B, C, VDRL and HIV as potential culprits?
    2. would the late course of PEP affect subsequent test results?
    3.though I cannot access pcr test and cd4 count in my location, what further test would you recommend if any.
    while I write you this, i am convinced am the rare case.
    thank you sir.

  17. Hi

    Please bear with me since I’m in a situation/position that I can not see a Dr for some discretion issues. All the info provided below is from self treatment and I need your opinion now.

    I had a risky exposure ( anal/vaginal unprotected sex for 30 min) with a sex worker and was started on PEP(Truvada/Isentress) for 28 day, 30 hours after the exposure. I have completed PEP and took a HIV ab/ag 4th gen test upon completion at a high end lab. I’m currently waiting for my results. Meanwhile I have a couple of questions:

    1- Does my exposure count as two sex acts? Since it was both anal and vaginal? I want to check out my chances of infection in the first place.

    2- I also took ” HBs Ag, HBc Ab, HCV Ab, HSV I IgG, HSV II IgG, HSVI,II IgM” . I was vaccinated for Hep B but it was a long time ago, hence the titr checking.
    Do I need to also test for syphilis and chlamydia or just take some antibiotics for it? I waited upon completion of PEP so there will be no effects from antibiotics on my treatment. Also because the antibiotics side effects might drive me crazy thinking it’s HIV symp.
    Is there anything else I should have checked myself for?

    3- How many PEP failures do you see in everyday practice with my regiment of PEP?

    4- I have some pimples on my butt but this happened after hair removal cream was used. Can this be HSV?

    4- IF my tests come back all neg (fingers crossed), soonest I can be 100% sure is 3 month after exposure or after completion of PEP?

    If there is anything I should do at this point that I have missed, Please advise.

    Thank you for the great and informative website.

    • As much as I empathize with your position, I must say that I do not condone self treatment. That is fraught with risks. Also, this platform is not for dispensing medical advice. So you should not and cannot act on any information you read here. You must still see your doctor. The answers to your questions are just opinions. They are NOT medical advice.

      1. I don’t see how counting it as 1 or 2 sex acts makes any difference to the risk.

      2. I cannot answer this question as it amounts to giving medical advice.

      3. So far none. This does NOT mean that the regime is 100% effective.

      4. I cannot diagnose you over the internet. You should see a doctor to find out if those lesions are HSV or not.

      5. Most guidelines still recommend testing up to 6 months although some say 3 months.

      • You couldn’t be more right and I agree with you. But this is the best I can do now and I appreciate your answers although you tried not to give medical advice over the net which is perfectly acceptable.

        The pimples went away. The tests all came back negative. And I was still protected for Hep B and no vaccine is required. Did another rapid test on day 35 with similar results.
        At this point I think I just have to focus on work and check myself according to guidelines.

        I would appreciate it if you can answer these two last questions at the best you can:

        1- Is my HSV test conclusive on day 28? Or do I have to retest because of the window for HSV?

        Anti-HSV 1&2 IgM -> Neg
        Anti-HSV 1&2 IgG -> Neg

        2-You said you have yet to see a 4th gen ab/ag test on day 28 after exposure (with taking PEP) get it wrong. It this still true?

        • I appreciate the fact that you accept that these answers do not amount to medical advice.

          1. Personally I also screen my patients for HSV at 4 weeks. However, there is scientific info to say that the HSV IgG can take up to 16 weeks to turn positive.

          2. Yes it is.

          • Hi Dr Tan,

            The 2 month HIV ab/ag 4th gen lab test came back negative. I’m more confident now that the 3 month mark will be the same.

            Is the 6 month test necessary or at 3 month, I can consider myself HIV negative and move on?

          • Not necessary. I think you can move on.

      • Hi Dr Tan,

        I don’t mean to accuse you but I’m confused about what you said above. When asked how many PEP failures you see, you replied: “So far none.”. But at the link below:


        You say that you have encountered a PEP failure.

        Can you clarify it for me?

        Many regards,

        • His question was specific to his regimen. The failure I saw in that blog post was on a different regimen.

  18. I’m a female. I had protected vaginal sex and unprotected oral sex with a straight male (no ejaculation). Got on PEP 64 hours after exposure. Completed 28-day regimen. 4 weeks after completion of PEP i had an RNA test/4th gen performed. Both neg. Another 4th gen test 6 weeks after the completion of PEP. Another 4th gen test 8 weeks after the completion of PEP (3 months post exposure). Can I finally move on? Thanks.

    • Yes you can. That said, I would remind you that some local health guidelines still recommend testing up to 6 months. You should verify this with your doctor.

  19. Hi sir I would kindly like to ask how conclusive is my 8weeks post pep 4th generation test.it came out non reactive. The truth is I took pep lalate by two weeks and tested beyond three months exposure. Your advice is needed please.

  20. Hi

    I’m a male and had unprotected sex with female SW both vaginally and analy. 40 hours later, I was prescribed Truvada as the only drug. Currently on day 16 and I only had sore throat on days 3 to 6 post exposure, no other side effects.

    1) Worst case, if she was positive, and with the above senario in mind, what are the chances of me becoming positive?

    2) Soonest I can get tested with conclusive results and the name of the test.

    • 1. There is really no logical or practical answer to this question.

      2. This differs between territories. Personally I would be very confident on a 4th Generation HIV test at 4 to 6 weeks post exposure but I will still repeat a 3rd or 4th Generation test at 3 months post exposure. However, this recommendation differs from practice to practice. The best person to advice you is your local doctor or the doctor who prescribed you the Truvada.

      • Hi

        Thank you for your prompt reply. I kind of know there were no answer but I was seeking a way for the peace of my mind. So I guess I only have to wait for the tests.
        1- Do you think Truvada alone is effective?
        2- How many PEP failures have you seen as you confront this everyday?

      • Hello Dr tan,

        I figured no one comes back here to actually post results so other readers can see what the outcome of their situation was.

        I got a 4th gen HIV ab/ag lab test upon completion of PEP (4 weeks after exposure) and it came back negative.

        Another 3rd gen rapid test on day 31 with similar result.

        My doctor was againt the test being conclusive and told me it is a good result but not at all conclusive. He said a 6 month test is. Do I really have to wait that long??


  21. After pep I did combo test and result was negative and once again 1month after pep I did 4th gen rapid antibody test and the result was also negative. Is it conslusive enough doctor?..will still test next month to make it 3 month but i am having serious panick attack worrying it might turn positve next month.

    • In my opinion your tests are as good as conclusive. You should still test at 3 months. Please see your doctor for further advice.

  22. Hi Doctor,

    I got on PEP 64 hours post exposure. After a 28-day regimen, I got tested for HIV with a 4th gen test–negative. At 4.5 weeks after pep (8.5 weeks post exposure) I got another 4th generation as well as an RNA QL test–both negative. Can I trust that I am HIV negative? Thanks!

    • Both of your tests are as good as conclusive. However, the guidelines still need you to retest at 3 months. Please see your doctor for further advice.

  23. Hi sir I was sex with Philippine house maid 3 week before. That time my condom broken. Now I am scared about HIV.so when I take test better. You give me your contact no.

  24. Hello doctors, is the 4th generation laboratory based combo test at 11.5 weeks post exposure conclusive, definitive. Thanks.

  25. Hello Doctors,
    My doctor put in a 4th generation Abbott Ag/Ab combo assay at 11.5(close to 12) weeks post exposure. The result was negative. Is this conclusive and 100 percent definitive?

    • I can only give you general information that the combo test is conclusive after 4 weeks. Whether or not is is “100%” depends on many factors that are outside my knowledge like did the lab make a mistake? was there a mix up in the blood? Was the machine faulty?

  26. Hello doctors, I took a 11.5(close to 12)week post exposure HIV test. This test was the Abbott AB/AG 4th generation immunosay test. The result was nonreactive/negative. My doctor said that the chances that I am infected are exceedingly low. Do yoy agree with my doctor and is this test conclusive. Also, are boils/pimples on butt symptoms of HIV at 11 weeks.

    • Generally speaking the combo test is conclusive after 28 days.

  27. Hi there.I would like to ask how accurate is the 4th generation test two weeks after post pep

    • Almost as good as 100% conclusive.

      • Thank u Dr Tan will do the test at 6 week’s post pep.hoping results will stay da same.I am nervous

      • Sori Doc’ would you recommend that I do both PCR and 4th generation duo at 6 weeks post pep and that would be conclusive enough.? Thanks in advance

  28. After having unsafe sex, i have started pep 56 hrs post exposure. Lymph swelling at jaw and armpit developed during pep and lymph at neck developed one week aftrt the completion of pep. Irony is even after 3 months after exposure (2 month post pep) lymph swellings are not vanished. All developed swells are existing till the time. ie 12 week.aftet exppsure.

    Mean while i have detected non.reactive on 4 th generation duo test carried out on 12 week after pep.


    • Hi, your results shows that you do not have HIV. You should see a doctor to have your lymph nodes swelling checked out.

      • Dear sir,

        Should I need to repeat HIV test. If required which test I have to conduct. ? And when I have to repeat ?

  29. does pep reduce viral replication and delay seroconversion?
    i m on pep and want to test abit earlier so is it alittle abit accurate?

  30. Please answer my question because I am so nervous. Is my 2 week post pep 4th gen Abbott test accurate?

  31. Hello Dr,please answer my question as I am very worried. 2 weeks after pep, my doctor did a 4th generation Abbott HIV test, and it came out negative. Is this conclusive and should i be concerned? Thank you so much.

    • It is not conclusive. But it is very indicative.

      • I am on prep after 50 hours of exposure…continue 14 days…and tested HIV duo…negative…. Is it early after pep?what’s the chance of positive after 4 week of exposure?..I am male with a vaginal exposure with a female..slight insertion unprotected… No ejaculation

        • Your test at 14 days is useless. Why did you even do it? What do you mean what’s the chance of positive after 4 weeks exposure? I really do not understand your question. And why are you on PrEP when you should be on PEP?

  32. Hello doctors, I may have been exposed 8 weeks ago through protected receptive anal and mutual unprotected oral sex with another man of unknown status. Approximately 48 hours after, I initiated PEP.2 weeks after pep, my doc placed a 4th gen abbott hiv test. The result was nonreactive/negative. Is this a good indicator and onclusive?

  33. Hi doc,

    Sorry to disturb, had sex with CSW condom broke, we both tested HIV (-ve). I was on PEP for 28 days and tested with 4th gen combo test immediately after. My result was (-ve) are the results conclusive. Please reply. very worried


  34. Hello Doctor,
    I want to know about the combo test, when to take it for sure and is it 100% conclusive and don’t need to text for another 3 and 6 month. thank you.

  35. Hi Doctor
    I had a rapid hiv test by finger prick after the exposure of 28 days and the result was negative (anonymous test at other clinic)
    Am kind of worried still as I heard from the doctor that the result was not conclusive as the antibodies might be found within 3 months.
    Which puzzle me why it is conclusive at ur clinic after 28 days of exposure?
    Please let me know if the result is conclusive or should i test after 3 months of exposure pls ?
    Thanks a lot

  36. Doctor, I asked you a question regarding my post pep test reliability. After a vaginal exposure with a CSW of unknown status ( suspected condom failure). I was prescribed Travuda only Pep. I have had 4,6,8 and 12 weeks POST EXPOSURE, HIV test reported Negative. All 4th generation, lab based tests.
    On 16th Week post exposure I developed a flu like illness, cough,cold. Does it have to do anything with my previous exposure. Or my tests are reliable, I should not worry??
    Do I need anymore testing??
    Please Reply sir!! My Doctor here said I dont need anymore testing.
    I need your opinion.
    Thank you very much.

  37. hi sir,

    I had unprotected oral sex and protected vaginal sex both for 1 minute… I took PEP on the 4th day

    30 days post exposure I went for Alere determine ag/ab 4th generation test (AIDS foundation) and came back negative..

    however, it still shy of 2 days of PEP dose to finish… is the negative result 30 days post exposure and 2 days shy of PEP completion a conclusive result?

  38. Hi sir I’m have HIV pcr DNA qualitative test ofter 28day result noon reactivate and common HIV test offer 4,6,8mnths result negative and ofter 9months HIV pcr DNA qualitative test result noon reactive and ofter12 months common HIV test result noon reactive but I have urine infection sir plz help sir I’m safe or not safe

  39. Hi Dr Tan, I’m curious. When you say the 4 week test immediately after pep is very indicative, are you referring to a duo test or to the Determine rapid test? Thanks

    • Dr Justin Sim

      This is the duo test.

      • Hi doctor,
        Would a duo rapid test done at 6 weeks post exposure (2 weeks after completion of pep) be indicative?

        • Dr Justin Sim

          Yes it is a good indicator but post PEP you need to do an antibody test at 2 months to be sure.

    • I had protected sex with a HIV positive lady. I usually bleed after I brush but she said she doesn’t bleed through her mouth; I also fingered her. Am I at any risk? She noticed her status 11 days after we had sex subsequently I was placed on PEP. 6 weeks after; at the completion of the PEP, I tested negative to rapid test and was told to come back at three months time. I am worried because here in Africa only rapid test is available. can rapid test be conclusive on 8 weeks after exposure; I am depressed and emotionally down. 5 days from now will make it 8 weeks.

      • Dr Justin Sim

        Ideally you should repeat a rapid test 3 months after exposure to be sure. Your results are reassuring and your risk is low with protection but repeat once more for peace of mind.

  40. Hi,
    Thanks for clearing doubts about HIV,
    I have one dout , I took pep with in 12 hrs after my condem broken duringnsexnwith a call girl.
    My base line test in negative ,
    My 3 month and 6 month hiv test also hiv negative .

    My question is , is that result conclucive and no need to worry about hiv.?
    Any possibility to occure positive hiv result after 6 month …
    Need ur urgent clarification , pls support .

    • Even very conservative guidelines say that a HIV test at 6 months post exposure with PEP is conclusive.


  42. Good morning doctor,
    i have done hiv dna/pcr and antibody test at 12week,HABg n HCV antibody,all are negative,could this be conclusive?

    then what other test am expected to carry out.because i still have mild headache and mouth thrust.

    my doctor says nothing is wrong with me but am not feeling ok though am on ciprofloxacine 500mg bd

    • Yes they are. I do not think your symptoms have got anything to do with HIV. If you are really concerned, you may want to get yourself checked for other STDs as well.


    • HIV antibody test is conclusive only after 12 weeks. If you are worried, you should get a combo test done now instead of waiting for 2 more weeks.

  44. Good Day doctor

    I have posted a question on the 23rd but I wasn’t replied, please assist me.

  45. actually it was 3 months and a week

  46. Actually 3 months and a week

  47. Hi, i had a negative 4th gen hiv duo teat 9 weeks after pep(30 days) is it reliable? the problem is that i had many symptoms and my blood report was was not normal. is it possible to have hiv symptoms for 2 months and still test negative? my doc says i am ok but i am stressed.

    • Dr Justin Sim

      It is a good result but you should test at 3 months after exposure if you have taken PEP. Abnormal blood results this early are not to do with HIV.

      • 9 weeks after pep is 3 months after exposure,, is it then conclusive? i had other symptoms witch started 2 months before last test. is it possible to have symptoms of hiv witch start 2 months before last test and still test negative if it is due to hiv?

  48. I completed PEP for 30days on 14th August,
    I was tested Negative after 5days after PEP? Is it ok?

    • Dr Justin Sim

      It is a good sign but you should repeat a test 2 months after finishing PEP to be sure.

  49. Hi Doctor,

    I just read The new UK guildline 2015 for PEPSE


    This guildline stats Hiv testing 4-6 weeks after pep finished ( 8-10 weeks post exposure) for conclusive results

    This’s draft document. I dont know how reliable?
    what do you think about this guildline? it’ll publish as guildline as soon right?

    for me , I am very happy to see this guildline.
    I just test negative with gen4 ab/ag and Nat after 8 weeks exposure
    How reliable of my results?

    sorry for my bad english hope you understand me

    Thank you and Best Regards

    • It is difficult for us to comment on whether this is reliable or not. However, what is stated there is consistent with the current practice (HIV test 4-6 weeks after completing PEP).
      Your results were conclusive.

      • Hello doc
        I had protected vaginal sex with a woman working at a massage parlour in Thailand
        Although it was protected, I am not too sure it broke or not as I was drunk
        The next day I went to the local clinic and requested for PEP and started Truvada at the 42nd hour and completed the 28 day course and tested negative on a combo test 25 days after completing PEP
        I have read some scary stories about PEP delaying seroconversion and I am still worried that I may be infected
        Please advise

        • You did the right thing by taking PEP after an exposure. If you are worried, I suggest you get another combo test on day 28 (from exposure).

          • Hello Doc
            Thanks for the quick response
            I got another combo test at 30 days post PEP completion
            It was an Abbot Architect Ab/Ag test 4th generation which came back non reactive
            Can I consider this as conclusive and move on?
            Please advise
            Thanks in advance

          • Technically the HIV Combo test at 30 days is conclusive. However, the best person to advise you on the accuracy of your test if the doctor who did it for you. There are too many assumptions we have to make in order to make a statement like that.

          • Thanks Doc
            I take your advice more seriously than any doctor in my country
            Please let me know what are the assumptions you make in order to conclude that I am indeed negative.
            The anxiety is absolutely killing me.
            Thanks in advance

  50. help...

    Hi sir Iam hiv pcr dna qualitative test ofter 28days results non reactive nd1st & 2nd screening test ofter 4, 6,8 months results non reactive nd 9 mnth hiv pcr dna qualitative test result nagitive nd 12 mnth common hiv test result non reactive. .I need any test sir ..pls reply

Thank you for your submission.

We will get back to confirm your appointment as soon as possible.