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.

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HIV Window Period

Are your HIV tests accurate?

HIV testing may seem very complex.

This is greatly due to the testing ‘Window Period‘. That irksome time from when a person is infected to when tests can actually detect a HIV infection.

Click here to read about the Biology behind the Window Period

HIV Signs and Symptoms

The HIV Window Period and Test Accuracy

HIV PEP Post Exposure Prophylaxis

This has caused a lot of doubt and worry with regards to the accuracy of tests done.

You might even be wondering right now how accurate your tests are.

There is a lot of confusing information out there. Some people claiming a window period of 2 weeks some people even saying 10 years!

This is because HIV testing technology has developed significantly since HIV was discovered in the 1980’s.

So a lot of information out there is out-dated.

Also, not the same standard of tests are available everywhere. This has caused different governments and different health authorities to develop different testing guidelines. So the reason why the Window Period is different in Massachusetts is different from Singapore is not because humans in the US react differently to HIV compared to humans in Singapore. It is because of local guidelines.

So what exactly if the HIV Window Period?

It depends a lot on WHICH TEST was done.

The following graph was prepared based on the latest information on Testing for the Diagnosis of HIV Infection.

HIV Testing Window Period for various Tests

HIV Testing Window Period for various Tests








Some points to note:

1. If you are within the first 10 days of possible HIV infection (aka the Eclipse Period), don’t bother doing any tests. There are NO tests that are accurate.

NB: If you are within the first 3 days of possible HIV infection please see us about PEP.

HIV Prevention within 72 hours of exposure (PEP) – Click Here

2. At day 10, the HIV-1 RNA PCR can detect HIV Viruses in the blood.

Remember that the RNA PCR test has a high chance of giving a false positive result.

If the RNA PCR test gives a report of less than 5000 viral copies per ml, it is likely a false positive.

Click here for information on HIV RNA testing at our Clinics

Also, the viral load may drop to an undetectable level upon full sero-conversion.

This is because the body’s immune system may have suppressed the infection to a point where there is not enough HIV virus in the blood for the RNA PCR test to detect.

3. Between day 14 to day 20, the HIV P24 Antigen will start appearing in the blood. This can be detected with 4th Generation tests (aka Combo tests).

This is why, although the official recommended Window Period for the Combo Test is 28 days, we are very confident when a patient tests negative at 2 weeks.

Remember that the P24 Antigen level will peak at about day 28 and becomes undetectable at about 6 weeks from infection.

This does NOT mean the 4th Generation (Combo) test is inaccurate after 6 weeks because the Combo test also detects IgM and IgG Antibodies (See below).

Click here to learn more about the Combo Test at our Clinics

4. Between day 20 and day 23, the IgM Antibody starts to become detectable in the blood.

This is only detectable by 3rd and 4th Generation HIV tests.

This is the other reason why even though the 4th Generation (aka Combo) test is supposed to be conclusive at 28 days, at 3 weeks when a patient is negative, we tell him/her it is as good as conclusive.

5. Between day 28 and 48, the IgG Antibody starts to become detectable in the blood.

This is detectable by 1st, 2nd, 3rd and 4th Generation HIV tests.

This will remain detectable in the blood for as long as a person lives. Therefore, doing a Combo test not only detects HIV infections that occurred recently, it also detects infections from years ago.

Click here for HIV Testing FAQ

More things to note:

The recommended 1st line screening for HIV infection is the Combo test NOT the antibody test.

So when you go for a HIV screening test, you should be asking for a Combo test. Take note that in Singapore the Combo test costs more than an antibody test.

The essential thing to remember about HIV testing is to get the RIGHT test done at the RIGHT time.

Come see us for professional advice on which test you need to do.

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

All Our Doctors are Fully Certified and Trained to conduct specialised STD and HIV Testing.

Your are welcome to visit Our Doctors at Our Clinics anytime during our opening hours.


Click Here for Contact Details, Address and Opening Times.
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Our Andrology and Infection Centre at Novena Medical Center is open.

Call us at 63972095 now to book your treatment.

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

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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.) Scotts Medical Centre (+65 6694 2348)

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



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.

If you have any questions, visit our free online forum on sexual health, HIV and STDs.More on HIV symptoms.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.We are now open on weekends.Related Articles:HIV CMIA Test AccuracyHIV ELISA and ECLIA testGetting HIV from Oral SexMore on HIV symptomsHow long can HIV live outside the body?Erectile DysfunctionPremature Ejaculation

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.




  1. Thank you your replay… dr tan

    Hi doctor….
    I am 26 years male. I am circumcised male. I am unprotected vaginal sex single exposer with a girl. Later 9 months found she is hiv positive.

    My tests:- 9 months post exposure westren blot negative.
    12 and 16 months postexposure Hiv rna pcrqualitative negative elisa,alerecombo,tridot,ictc all are negative 22 months time period and 70 all hiv test total….

    my questions:-

    1)Exactly 22 months after a risky exposure (sexual encounter with female possible IV user) I took a full STD panel (including an anti-HCV test). All results were negative. any further test needed….

    2)Some places say it takes years to detect antibodies for Hiv, Who should I believe? Please let me know if I can trust my results!

    3)iam negative…
    Pls doctor say clear answer all my questions….
    Your the best…
    Thank you…

    • Hi dr tan

      Iam waiting your replay…
      Iam negative..iam move on my wife make childrens pls..tell me…

      Thank you again sir….

  2. my questions:-

    Exactly 21 months after a risky exposure (sexual encounter with female possible IV user) I took a full STD panel (including an anti-HCV test). All results were negative. Some places say it takes years to detect antibodies for Hiv, Who should I believe? Please let me know if I can trust my results!

    2)How to removed my brain hiv fear pls iam goings to mad…pls

    Iam negative any test nedded

    • Your tests are conclusive. There is no reason why you cannot trust your results. If you are having persistent HIV anxiety, please see a psychiatrist or psychotherapist.

  3. hi

    I would like to ask what is the appropriate test 20 months after exposure to confirm hiv status?

    i’ve done cmia and elfa hiv duo ultra in previous months.

    is 20 months negative test using 4th generation test is conclusive?

  4. Prathap

    Hi doctor….
    I am 26 years male. I am circumcised male. I am unprotected vaginal sex single exposer w a girl. Later 9 months found she is hiv positive.

    My tests:-
    Hiv rna pcr qualitative,westren blot,elisa,alerecombo,tridot,ictc all are negative 20 months time period and 70 all hiv test total….

    my questions:-
    Exactly 21 months after a risky exposure (sexual encounter with female possible IV user) I took a full STD panel (including an anti-HCV test). All results were negative. Some places say it takes years to detect antibodies for Hiv, Who should I believe? Please let me know if I can trust my results!

    2)How to removed my brain hiv fear pls iam goings to mad…pls

    Iam negative any test nedded

  5. Hello Doctor, I had unprotected sex and I got gonorea, 3 weeks after exposure I got severe fever and swollen parotid gland in the righ side, I went to doctor and he said that virus entered to my body, he gave me anti biotik, severe fever remain in a week and the swolen parotid glad disappear in 10 days, I got tested CMIA ag/ab 23 days (negatif) and 28 days (negatif), am I free from HIV even I got symtoms.
    Thank you, I hope your best answer and advise

  6. Hi, may I know after sexual how long test result is accurate?

  7. Hello Dr.,

    I had a possible exposure where I am unsure if he ejaculated into the condom, so I have been taking oraquick oral swab tests at home at week 7 and it was negative. I then took a oraquick advance oral swab at 8 weeks and it was negative. Is it true that the oraquick advance swab is third generation and therefore conlusive around 9 weeks? I also took another oraquick advance swab at 76 days, which also came out negative. Is this conclusive? I was only 8 days away from 12 weeks. Your advice is greatly appreciated.

  8. Dr greeting from malaysia. 7 days ago i had an exposure with csw. First of all my purpose go there is not for sex. Just wanna talking and having a chatting. For all the way, what i recall there are not sexual involved. Just i reply my message, phone call and pass bnk note to her and she are the one opn the door for me. Dr fyi. I nvr take any alcohol and without touching her or she touching me. She also nvr take out any clothes snd me too. Dr if i wanna to a test at 10days after exposure. Cn i do pcr rna test hiv ?

  9. noreen sax

    Hello Doctor,
    I am sorry to bother you. I have a non-sexual related question about HIV. There were two incidents.I was in a foreign country. I ordered Oysters, in a place where everybody was eating Oysters. The man opened the Oysters without gloves. I checked to see if there was any blood blood, and I could see no blood.. And then 5 minutes or so later, I ate the oysters. I was wondering if this could put me at risk of HIV if the person actually cut his hands while opening the oysters.
    And then two weeks later, this lady opened a open bottle of wine, and removed the metal cover, and I wonder if she cut the fingers while opening it, could one get HIV from any blood if it had it.
    I ask this because of 2 weeks after the incidents. I started to have VERY LIGHT night sweats. With sweats around my neck. THis happened now 3 days in a row. I sleep in a room that is a bit hot, and it gets about 80 degrees before it cools down at night to 71 degrees with airconditioning, which turn on just before I got to bed. It is NOT drenching night swears I also have enormous muscle pain under my left arm, and it hurts really bad. I am really scared. DO I NEED to be tested? My own doctor said this is not a concern. thanks so much

  10. Dr sorry i was in trouble again. But what i recall is without any sexual contact, i never take out my clothes, touching the girl as well. I just seat there. That us what i do at there. The girl also no thouching me and i was confirm with her through phone and she also mention nothing involved just conversation only. Dr can i conduct a hiv rna pcr at 10 to 14days after exposure conversation. Dr am i at risk?

  11. Hi doctor please help a soul.I had unprotected sex with a guy and I had an alere determin test at 47 days after and it’s negative please how conclusive is this because I’ve been living in fear, feeling weak no appetite and all and feeling somehow thanks!!

    • Dr Elaine Loh

      Dear Shola
      A negative alere determine test at 47 days is a good indication, but best to repeat again at 3 months post exposure for absolute confirmation.
      Do come in and speak to our doctors if you still have further concerns.

  12. Good day Doctors,
    please assist me, i’m a female and i had sex with my new boyfriend and the condom broke. i asked him to do an HIV test because i was scared, he did a rapid test and sent me the pictures of him holding the negative test, 2 weeks after i developed some symptoms.
    1. flu with tension headaches
    2. right side of my neck hurts and i think the lymph node is swollen
    3. bloating and constipation
    4. itchy eyes and skin but no rash
    5. yeast infection and bv
    i had a combo test done 27 days after exposure, rapid test 30 days, rapid test 48 days all test are negative are my results conclusive.

  13. dr recently i was test for my last exposure (protected sex) at 4 weeks, 5 weeks and 9 weeks and 11 and 12 weeks. all use combo test and all negative and hcv pcr rna test at 5 weeks (qualitative test) and 12 weeks antibody test. dr can i move on from the exposure? and dr the lady also done a test at 27 days after my exposure which is also negative. so can i move on?

  14. Robert

    Hy, i had protected sex with an older transsexual. We are both from europe. We had sex 2 times, she gave me oral unprotected and rimming, i was protected when i was having sex with her, therefore i was insertive. 3 days after the event i had diarhea for 2 weeks and loose stools after that. At 12 days my cough started that went on for over a month and a mild sore throat. At 12 days i had a combo test Hiv1/2/0,Hcv(Architect, clia method), to establish that i wasnt infected previously. After that I had Rna NAT (tma method – qualitative) for Hiv1/2,Hcv at 16 days. At 45 days i had the combo Hiv1/2/0,Hcv (architect – clia method) test again. Everything was negative. The woman(ts) also showed me her Hiv1/2,Hcv elisa antibody test results that she had 3weeks before our meet, because she had an operation and she had to be tested. She told me that she didnt have sex 4months prior to testing, and that the last sex ahe had was with her previous bf 4month before her test, she isnt an escort. People can lie of course and i cant be certain of her status. My question is,how reliable are my results? I need to get a conclusive test at 3months, but im super stressed now and cant function properly, im suicidial and constantly thinking of ending my life.

    • I would consider your test results conclusive – no HIV.

      • Robert

        What if i fingered her with a condom on my finger,but when i applied the condom on my penis the condom would turn inside out? Are the test results reliable even if that happened?

  15. Window Testing

    Hi, Doctor.

    I know that the a combo test is not conclusive until 28 days after a potential exposure but will a test at 20 days be a good enough indication? I tested non-reactive on a combo test at 20 days, but on day 22, started having icepick headaches. These went on for about 3 days. On day 25, I started having post nasal drip which led to some very very minimal dry cough. Today, day 28, I have a mild sore throat from all the throat clearing (from the post nasal drip). Do these symptoms look like ARS symptoms? I know I should get tested again but I just want to know if my 20-day test is at least a good indication of my status.

    • Dr Elaine Loh

      A negative Combo test on day 20 suggests that you have not been infected with HIV. However, you should get it repeated after 28 days.

  16. Carlo

    Hi Doc.i have a protected sex exposure with the sex worker. I feel worried I took hiv test on my 59th day post exposure it came out negative (Sd bioline 3.0)
    66th day post exposure CMLIA (4TH GEN) NON reactive
    75th days post expsoure non reactive
    Is my 66 day non reactive result is conclusive? My worried is after i got my result on my 66 day post exposure hiv test i have sex with condom with my girlfriend my worry is am afraid that i may infected her.

    • Dr. Julian Ng


      I assume the HIV test you did at 66 days post-exposure was a Ag/ Ab 4th Generation test. If so, then the result is conclusive.

  17. Ahboy

    Hi,dr if have hiv can take work permit in singapore? And the singapore use what generation? If i have 3test 1st is at 20day ,34 day,75day all no reactive mean ok? First and second is at malaysia test ,the last is at singapore i do the work permit ,is that i ok? Or nid retest? Thk for help

    • Dr. Julian Ng


      Generally, if someone is on work permit and is confirmed to have HIV, the work permit would normally not be approved or it would be revoked. As for testing for HIV, when you apply for your work permit, that would have been tested. as to whether you need to be retested, you will need to discuss with your doctor especially if you have particular risk exposure.

  18. Hi Doctor,
    I met(with protection) a girl on 6th October 2017, after a way week I feel so many changes in my body , like weakness, headache(24 hours) , mouth ulcer. I waited a 66 days and went for testing HIV 1/2 (AG & AB). its came as not detected. after that also I am facing same symptoms , I just worried and again went for screaming after 160 days, its came as not detected. but still I have all the symptoms mentioned above, I can see vertical black line on my hand nails and near elbow two glands are paining, one more thing on November I bit reduced my weight now again increased. kindly suggest me what I can do further , can I go for HIV RNA test ? kindly help me on this

    • Dr. Julian Ng


      Your HIV results are conclusive. your symptoms are NOT due to HIV, however you should still seek further medical attention for your ongoing symptoms as they may be due to other medical conditions.

  19. Hi Doctor,

    I had protected sex with a massage lady overseas 4 days ago. I was tested HSV positive a few years back and had outbreak every now and then on my genital area. Since 2 days ago I experienced extreme fatigue, nausea, tingling sensation and numbness on my hands and feet. I would like to do a gen4 HIV test on the 14 days post exposure to ease my anxiety. May I know if the test would be a good indication as the anxiety and the current symthoms is killing me.

    • ARS symptoms will not develop after 2 days, so that can be reassurance enough. However, if you are still concerned, you can come down to our clinics for testing – 2 weeks post-exposure would be a very good indication, but for conclusive results we would advise a repeat test at 28 days onwards.

  20. Biplob ghodh

    HIV 1/2 25 days and 41 days negative conclusive at 58days no symptom

    • Dr. Julian Ng


      I assume you are using the 4th Generation HIV test for testing. If so, then your test is conclusive after 28 days post-exposure.

  21. hi sir..

    what is the hiv window period ?
    some doctors say window period vary confused….
    take test every 3 months I am not sexualy active.
    I am do only single exposer.
    9 months offer exposer alere combo test negative..

    pls say what is the exactly hiv window period.?

  22. Hi sir..

    I read the internet some people don’t develop antibodies in many years….this type of persons which test to detect hiv absence or percent conformation….

    The 4thgeneration hiv test 3 months accuracy 99.9 and my result negatve 17 months post exposure it’s mean 100% accuracy…

    Iam free from hiv infection..

    Iam start my new life… without hiv fear…

    Thank you..

  23. Charles

    Dr i got an question to ask as i very worried about that. As i had done alot of test and i am very tired for that ad. Or maybe you cn give me a good explaination. I had protected sex with a girl. Just done a combo test after the window period. However i was saw hep c co-infection and sero-negative. So i was really scare that the combo test and pcr rna test will no be conclusive for over come the issue. Really i feel tired to ask and seeking more test ad. Pls help thks

    • Dr. Julian Ng


      If you have Hep C infection, it can cause a delay in seroconversion of HIV.Thus, if you are concerned whether you could be Hep C infected, please visit a doctor for further evaluation. If you are found to be Hep C infected, then window period for testing will likely need to be extended to 6 months.

      • Charles

        Thks dr julian. But cn the 4th gen test still able to detect it? Or any test can detect it?

  24. Dr.tan..

    Plz reply me doctor your silent I’d killing me daily ur reply all the person questions y not for me

  25. Hi sir…

    Pls give me your valuable replay….
    Iam full load anxiety…..

    This year june iam get married pls help me sir….

    Iam free from hiv…

    Last question

    Thank you sir..

  26. Hi doctor tan
    I am 26 years male. I am circumcised male. I am unprotected vaginal sex single exposer w a girl. Later 9 months found she is hiv positive.

    17 months post exposure , 4th generation alere combo hiv test negative.
    My question:
    This year june I am get married make children’s happy family.
    pls clarify me I am 100% negative.

    One doctor told me hiv windowperiod 3 months to 10 years.take hiv test every 3 months..

    Iam 100% negative…
    Pls answer my question….

    Thank you your replay….

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