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.

All prices quoted below excludes prevailing GST

We are Open on Saturdays and Sundays.

Click Here for Contact Details, Address and Opening Times.


We have 5 locations conveniently located at Robertson Walk, Bencoolen Street, Novena, Scotts (Pacific Plaza) and Somerset (H&M)

Robertson Walk          6238 7810   map

Bencoolen Street        6884 4119   map

Novena                           63972095   map

Scotts                              66942348   map

Somerset                       62620762   map

Email: doctor@drtanandpartners.com



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.

Consultation $20.00-80.00
Rapid test only $20.00
(not inclusive of test)
8am – 5pm $60.00
5pm – 9pm $80.00
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 $ 190.00
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. just ask

    doc you said some people said 10 years window period… from the time that elisa started for testing people it was up to 1 year.. it never was 10 year..you realy heard someone saying that???

  2. doc you said some people said 10 years window period… from the time that elisa started for testing people it was up to 1 year.. it never was 10 year..you realy heard someone saying that?

    • Obviously whatever that “someone” said is questionable. We are just giving you an example how reading stuff on the internet can confuse you.

      • just ask

        thx doctor but you said that hiv testing technology has chanegd significantly so it is like you re saying that older with more inaccurate tests window period was more than one year.. is that what you mean doctor..pls answer me i m realy stressed :/ 🙂

  3. Dr.Tan you and your team are doing a great work. Thanks in advance. Plss answer my question below.

    Even during PEP p24 antigen testing window period is same.

  4. Hi dr tan and partners,

    1.I know window period is 3 months as they say…. but say you tested NONREACTIVE at post 9weeks, a tad 3 days short of 10weeks using a 3rd gen antibody test. is there a chance that the results will still change at the 12th week period???just curious..
    2. regarding syphilis test, a negative TPPA result and a non reactive RPR at 9 weeks, is it a conclusive result already??

    thank you in advance

    • 1. Antibody test is only accurate after 12 weeks. I would take your result post 9 weeks as a good indicator that you are HIV negative, but you should still get a repeated test after 12 weeks.
      2. Yes. If you are concerned, you can also repeat in after 3 months.

  5. After penis vaginal rubbing with a massage girl I was put on PEP from 40th hour. RATLEGRAVIR+TRUVADA.
    Even during the PEP p24 antigen test window period is same.

  6. satinder

    but sir , you didnt answer me. is delayed seroconversion possible with latest tests ? and is six months test conclusive in all rare cases too ?

  7. satinder

    Dear doc,
    I was worrying about possibility of late hiv seroconversion ? Is it possible with fourth gen tests and has you ever experienced it in your practice ? My exposure was protected sex with csw and my test was neg three months later….

  8. Satinder kumar

    Dear doctor,
    I want to know if delayed seroconverion is possible by use of fourth generation tests and has it ever happened in your practice ? I am really worried about its possiblity. My exposure was protected sex with csw (in her period) and my result was negative at 3 months (combo test). please help sir. I have a very weak immune system so I am asking about its possibility ….

  9. Hi, just wanted to know whether the window period for a needle stick injury is also 28 days for a 4th generation combo test? This is without taking pep.

    Is there different window periods for different exposures or do sexual and non sexual have the same window period. Thank doctor

    • There is no difference in terms of window period.

      • Stickguy

        Thanks doc. Just on that note out of curiosity, could yhe window period and time for infection change if exposed to a stick with a low viral load as opposed to a high viral load (Eg. Would the low viral load stick take longer to test postive?) Or is infection an infection either way without an effect on window period.

  10. Good day,

    I’ll try keep this as short as possible, without questionable queries.

    – I had taken two consecutive HIV rapid home tests, HIV 1/2. They both turned out negative. They are both 45 and 47 days (post exposure) respectively. Is it safe to assume that it is HIV Negative?

    • Second Query:

      Hopefully this isnt absurd, but presuming that is isnt: I had gone to rather “dodgy” gay sauna lounge. I had walked around barefooted and by the time I had gotten home I realised that I had a minor injury on my toe when I stumped my toe at the lounge. No severe bleeding, could I get infected if i stepped on semen with a viral load

    • No. HIV 1/2 is only conclusive after 12 weeks.

  11. HI doc iwas expose to unprotected sex last july 17 and got tested sept 9 and the result is non reactive the test used is EIA and GENSCREEN ULTRA hiv AG/AB is that already conclusive i am still scared cause im still feeling some sympthoms or is it because of my anxiety do i still need to get tested.. thanks and godbless

  12. hi doc i was expose to unsafe sex last july 17 and got tested sep 9 the test was non reactive using EIA and the kit was GENSCREEN ULTRA HIV ag/ab is that accurate or do i need to get tested again cause im still anxious and still feeling some sympthoms thank u in advance god bless

  13. Dear doctor!
    I had a sex with hiv positive woman.
    I did a PCR RT qualitative at 10 days and PCR quantitive at 17 days and also I did 4 gen lab tests at 20 and 25 days, all tests was negative. Can I consider my result as conclusive. Thank you

  14. Hello Dr,

    I had unprotected anal sex, I was the top.
    I had a 4th generation test done at day 21.
    Should I get another 4th generation test done at 28 days?

    Thank you

    • Yes you absolutely should. Although I can say that your 4th Gen test at 21 days is already very accurate.

  15. Hi doctor, tested non reactive at 35days or almost 5 weeks.. The test was done using HIV 1/2 EIA-3rd generation.is this a good indication of my status? Hope you reply…im really anxious for more than a month already..

    • Yes it is a good indicator but not conclusive. You have to repeat this test at 3 months.

      • Wow. Now im scared dr. Tan. I thought a 3rd generation test at past 4weeks is accurate already…and it seems to conform the illustration above. So meaning dr. Tan, There’s a potential that the results will still change..???

        • You are coming here asking us to verify the accuracy of your test results. In all fairness, I do not think that is fair. There are too many assumptions we have to make. You do not take a dish cooked by another chef to a different restaurant and ask them to verify that there is no seafood in there do you? The best person most familiar with the performance characteristics of the test done for you and your clinical risk situation is the doctor who conducted the test for you. And you should ask him to verify the accuracy of your test. From our point of view, we have to take a very conservative stance and say that the 3rd Gen test is not officially conclusive at 4 weeks. Which is backed by current scientific evidence.

  16. Hello,
    I had a nude body to body massage and i fear about hiv from fortting and i paranoid about the possibility of seconds of penetration as she was rubbing her belly though she doesn’t agree to that .
    I had symptoms and since 3rd week im having balls in my neck and white tongue.
    I tested myself at 5 day eclia o.028 negative
    23 cmia combo p24 negative 0.05
    31 cmia combo p24 negative 0.09
    41 cmia combo p24 negative 0.19
    Still on day 60 i feel balls in my neck and white tongue while my doc said to forget about it but i doubt him as a hiv specialist because he’s a family doctor.
    Do i still need any further testing or 41 days is conclusive ?

    • Generally speaking a Combo test should be conclusive after 28 days. Please verify the accuracy of your tests with the doctor who did it for you.

      • I just tested at a lab ( dr lal path lab , india ) it is to be known as one of the reputed labs in india. I know doctor you are really busy to reply for these posts. But i fear swollen lymph nodes , please tell me do i need to retest again ?

        • Please see my reply above to Anximan. You should be bringing this question to your doctor instead of us.

  17. I did an oral sex six months ago. I did not feel any symptoms during the six month period but I decided to do HIV 1/2 antibody test only after 6 months. The result was negative. Is the result conclusive? Do I still need another test? Is the risk higher that I may have HIV? Thanks.

    • In my view it is conclusive. But I do not think it is fair that you come to this platform to verify the accuracy of your test results. There are many factors that I am not privy to like what kind of test was used, was the test conducted properly etc etc. So the best person to verify the accuracy of your test results if the doctor or medical staff who did it for you.

    • Do you have responses already?

      • Thanks Doctor. The test was the rapid fingerprick blood HIV 1-2 Antibody Test. I read articles that such test is accurate and conclusive. And I just want to have further confirmation from your end.

  18. Good evening doctors.i have some questions to ask .i kindly please u to answer if is posible.at 6 mounth and 1 week from an exposure i ve done 2 test elisa ag ab and eclia ag ab both in that day but different labs.both negative.at 11 week s and 3 mounth also negative.but i have symptoms. From week 1 after exposure i have gastric refluxe.some days not some day s yes.i took a test for helicobacter pylori also negativ.risk was protected sex vaginal with a csw.after removing condomn i think i ve touch my penis and inghinal.shaved zone .i woul d like to ask.is necesary to repeat the test.?could this test detect hiv 2?posibility for other disease??others std are negativ.hepatities negativ.my girlfriend haded 2 days stomach pain .and after the pain an acid reflux.i gibe something to she?thank you

    • I do not think your symptoms are related to HIV. If you are concerned, the only way to ease your worry is to get yourself tested again just to be sure.

      • Butt i have 4 neg test 4 generation.1at11 week s .2 at 3 mounths.3.2 in same day at 6 mounth and 1 week.

  19. I have 7 weeks 50 day antibody terst negative and 8 ,9 weeks fingerprick test now iam 9 day to my final 12 weeks of my last exposure iam very scared please help me

  20. Hi doctor.
    I had a blowjob from my girlfriend.am i at the risk of HIV being transmitted to me.she says she is not hiv+.

  21. Hello dr
    First of all tnx for all your responces…
    A gay man fingered my anus about 36 days before and from that day i start to worry about hiv
    I tested a pcr rna at the 15 days after that and come negetive
    At 27 days i test combo ab/ag with ecl method and it came negetive
    And after a month i tested with 4 th genereation elisa ab/ag and again come negetive
    Do you think my test is accurate?
    I think that that guy may have blood on his finger because his fingernai…

    • In my opinion your tests are conclusive. Please verify this with the doctor who did the tests for you.

  22. Jon Son

    Dr. I did handjobs with my partner. His semen gets to my eyes and I received a oral sex from him. It was tested 7 weeks after my exposur and its non reactive. I’m so worried.

    • The accuracy of your test at 7 weeks depends on what test you did. Please verify the accuracy with the doctor who conducted the test for you.

  23. Shadrach

    hello, I received a handjob from someone whose status I don’t know ,negative 4th generation test at 30 days would you say its conclusive

  24. I got tested 23 days after exposure and it was negative with the HIV ab/ag 4th generation test. Should I get tested again, I’m shaking up

  25. I had a negative 4th generation Elisa on 25th day after hand job with unknown person wat do you think

    • I think it is not possible to get HIV from a handjob. I also think the 4th Gen test is only conclusive at 28 days.

  26. Hye dr, i have done a hiv test on 37 days with eclia test, and the test become negative, was that conclusive?

    • In my opinion it is not and should be repeated at 3 months. Please verify this with the doctor who did it for you.

  27. Hi Doctor,

    I did an ECLIA 4th Generation (Combo) test on 25 th day after exposure, and the result was negative.

    Can I consider this conclusive or should I depend on the PCR test?

    Thanks for the support 🙂

  28. Hello doctor,Im male 25 years from italy , I did two test at 35 and 43 days , both 4 generation, do you think I can stop thinking about hiv? Are conclusive ? Im really worried

    • In my opinion you can certainly stop thinking about HIV. Please verify this with the doctor who did the tests for you.

  29. Hello Doctor
    I am 28 male.
    I had unprotected vaginal sex on 24 June.
    I am worried.
    So I had hiv 1 and 2 duo p24 ag/ab test twice.
    One is at 4 weeks and other at 6 weeks.
    Both are negative.
    0.09 and 0.08
    And I also had pcr rna test that is also negative with cdr4 count 582 and all other parameters are normal.
    But I have pain in my lower legs from the day I had sex 24th june.

    I am very tense.
    Please guide.
    What my results show.
    Can I trust them.

    • In my opinion your results conclusively show that you are not infected with HIV. Please verify this with your doctor and also ask him/her to work up the actual cause of your symptoms.

  30. Hello doctor
    I had an unprotected vaginal sex on 23rd June.I am worried so I did hiv 1 and 2 combo p24 ag/ab test at 32 days i.e on 25th June,it was non reactive 0.009. After 40 days I had pcr rna test done.reports are
    Absolute lymphocytes count-1512
    CDC (t cells)-77.63
    Absolute cd3-1173
    Cd4(helper T cells-38.51
    Absolute Cd4-582
    And quantitative rna report is awaited today.
    What my results show.
    I am very tense and depressed.
    Plz help.

  31. I did hiv 1-2 AB antibody test after 44 days of
    get infected can i get true results

  32. Gaurav Sinha

    I am male 29, had a protected oral and vaginal sex with SW 20 days ago in India. My Condom didn’t break and remained intact during the entire episode. I have even changed the condom after oral sex to ensure that its not broken. I was heavily drunk and made this mistake which has turned my life upside down. Under enormous stress which has reduced my appetite and concentration. I have got myself tested with HIV 1&2, P24 EIA Combo test at the 17th day. It was non reactive.I do not have any symptoms apart from a little sore throat. And I know that this test is non conclusive before 28 days, However my anxiety is killing me badly. Is there any test which I can go for right now in order to put an end to my stress. Can I assume my 17th Day negative result as little assuring and what are the chances of me getting infected.

  33. Gaurav

    Hi Doc,

    I had an episode of protected oral and vaginal sex with a SW in India. My condom did not break and stayed intact during the entire episode. my HIV 1&2 with P24 antigen test came out negative after 17 days. I know that it is only conclusive after 28 days, but I am too stressed out to wait for that long. Is a negative combo after 17 days optimistic in my case?

    • You risk was very low. And test the combo test at 17 days is very indicative. I do not think you need to be too worried.

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