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.


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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. WorriedMan

    Hi Doctor Jonathan or Tan

    I had unprotected sex with an NRI woman on January 23, 2018 early morning (or midnight) about 5 times and 1 time in the morning.

    Now, yesterday, on February 21, and today on February 22, 2018, I went for a 4th generation antibody and 4th generation Duo Combo test respectively. They are 29 and 30 days respectively. Both are negative and non-reactive.

    The woman in question since returning to her country got heavy DVT/PE and keeps coughing since. It has been two weeks. She returned to our country again and was sick like a dog. She was on blood thinners.

    Now, she reports a sharp and unbearable headache with ENT complications during take-off and landing. She feels dizzy, fatigued and unable to walk at times. Coupled with that she had dysuria during menstruation and many other symptoms.

    The female AIDS survivor (Jennifer Vaughan) who became famous on YouTube also said that she had severe stabbing headache during take off and landing. So, I would like to know if these could be late stage HIV symptoms?

    And what about my results doctor? Were the right tests taken at the right time? Are my results conclusive? Please reply me as early as possible. Thank you doctors!

    • HIV symptoms are non-specific, and can be due to multiple other conditions. I cannot comment on HIV probability just through symptoms. I would consider your results conclusive though, so I would not worry if I were you.

      • WorriedMan

        Thank you very much Dr Jonathan

        I found myself another reason to worry though. The 4th generation test was a home blood sample collection from a lab.

        The guy took out a syringe pack in a cover and tore it open, which I saw but since I was a few feet away, and didn’t personally touch it, I feared I would contract it through the syringe. The lab technician reassured me enough that it was new.

        While filling it in the tube, he also sort of exposed the blood to air. So…

        1) Should I go on PEP again due to fear of the syringe? I was on PEP till the 30th day, beginning at 67.5 hours.
        2) So, even with PEP, 30 days is conclusive?
        3) Does exposing the blood sample to air dilute the result? Or change it in any way?

        Sorry for wasting your time. I have a lot of OCD as well. Can you please reply Dr Jon? I promise this is my last.

        • No, I would not consider PEP for the testing itself, otherwise you will be paranoid forever. Testing at 30 days even with PEP is essentially conclusive, although guidelines will still recommend one more at 3 months for precaution. Exposing the blood to air in that way will have no impact on the result. Move on with your life.

          • WorriedMan

            Wow! You gave me the breath of my life back Doctor.

            //Testing at 30 days even with PEP is essentially conclusive// You have said it all on that one. Yes, I will do the confirmatory test at 3 months. Thanks a lot Doctor. Moving on 🙂 Thank you 🙂

  2. jean paulo

    Test after 52 days 4th generation, is conclusive

  3. Hello doctor I had kiss with a dance girl on 8th Dec 2017 I just swalloed some saliva from her mouth I don’t know whether blood was there or not. My 4th gen test gave negative results on Jan 6th 28 days is it conclusive I am bit worried because I am facing some sore throat and oral thrush symptoms

  4. Doctor. At the 10th day, I have been diagnosed syphilis and tested HIV combo test “not detected”. I tested it again HIV combo test at 28th day, it was “not detected” too. The titre for my syphilis 1:32 at 10th days drop to 1:16 at 28th days after taking antibiotics tablet. Should I consider my HIV test conclusive at 28th day?

  5. Are all 4th generation test for HIV (Cmia, elisa, eclia) conclusive at 28 days?

  6. Good day doctors,

    I went to a massage parlour in malaysia for a hand job during wee hours on 6th Jan. In the process, I fingered her. After ending everything, she used a wet tissue to wipe my finger after which she used the same tissue to wipe my penis tip. What are the risk? I took a 4th gen combo test on 27th Jan noon time and tested neg. Should I retake? Thanks.

  7. Hi doc i got a non reactive ag/ab test at the 31 day post exposure

    accordiing to the clinic it is 4th generation

    is it conclusive ?

  8. I have hypothyroid as well.will it affect results.please guide

  9. First of all doctor i would thank you for helping people.i have read your comments and feel reassured.my question is that i gave blow job to unknown hiv status guy.i am not sure whether he came in my mouth or not.I got tested by local lab which hiv screening panel test( hiv 1 2 antibodies p24 Ag combo)that 4th gen assay performed by cmia technique on abott platform.test results are
    21 days index 0.11 non reactive
    42 days index 0.11 non reactive
    55 days index 0.23 non reactive
    Pl tell me is my result conclusive and i dont have hiv.why has index value increased.i am really worried.please reply as soon as possible?i am afraid about spreading hiv to my family members

  10. hi doc..i hv done hiv combo test(cmia) at private hopsital.
    hiv ag/ab on 17th day – non reactive
    hiv ag/ab on 20th day – non reactive
    ill do it again on 28th day for sure….do u think its a good indication for me to get it back negative?

    • And i did hiv ag/ab + p24 (elisa) on 22th..not detected and non reactive..how should i take this doc?pls guide me

  11. Hi doc,

    1st test (34th day) – HIV I & II, antigen and antibody screening – NON REACTIVE

    2nd test (56th day) – Rapid, 4th gen at your Bangsar clinic – NEGATIVE

    3rd test (64th day) – HIV I & II, antigen and antibody screening – NON REACTIVE

    All results conclusive?

  12. Hi. At day 44 after my last contact i did a hiv test it reads: test name; ac anti hiv duo result 0.09 ;reference 1 positive; result in words negative. Do you think this result is gonna change after 3 months. Thank you.

  13. Charles obss

    Hi. I got a test 4gen at day 28th. Some hours after ends day 27 (around 6) its means during 28th day and not after it.

    Can i be calm with this test and move on.?



  14. Hi doc..on 22/12/17 i went to a massage parlour.the masseur(man) about 46 years old massage my body..suddenly he penetrated his erected penis into my anus..tat was about 5 to 6 seconds..then i ask him to pull out..condomless..was very brief and short..no ejaculation..i was truly worried abt my hiv status..went through sleepness night for few days..on day 17th ( 7/1/18) i did my combo test hiv ab and ag test..came out non reactive..how should i take this?pls help me doctor

    • Day 17 testing is a good indication but not conclusive. Please repeat one at 28 days or more.

      • Thanks 4 ur reply doctor..based on my exposure..do u think ill be getting hiv..so worried and anxious?

  15. Hi,doctor i have a protec sex with a sex worked and i dont know the condom ok or not affter that i have 2time hiv test 1st is at 20day hiv 1/2 ag+ab elisa no reactive 2th is at 34day p24 ag+ab screen the menthod is wesrten blot is that means i ok? 2018.11.11 is my weeding now i very scare i got hiv ,the 1st time i also got test vdrl no reactive ,tpha negative is that mean ok?and the window period how long ?thank for help

    • The test at 34 days is conclusive, no HIV. The syphilis testing is a good indication but only conclusive after 3 months.

  16. Hi dr, Im just test HIV Rapid Duo test at your clinic at KL. Its exactly 22 days from exposure. My exposure is unprotected cunnilungus and vaginal sex(protected). Result negative, Should I re test again?

  17. Worried Guy

    Hi Doctor
    Happy New Year…..
    I had done protected s*x with Unkwn HIV status lady. After a week I experienced flu symptoms like 24 hours headache , mouth ulcer , chill , muscle ache . I got worried and went for HIV 1 & 2 (Ag & Ab) test after 68 days it’s came as negative. But she still I have same headache (24 hours) , muscle ache and mouth ulcer. No fever at all.
    Kindly suggest me on this? Do I consider this test is conclusive? Please help me on this doctor.

  18. Hi,dr i have protect sex with a sex worked and i dont know the condom have break or not have u see a 28day hiv 1/2 p24(ag+ab) no reactive affter charge positive? My wife plant to have baby so dr your opinion can i move on or still in the window period?

  19. Dear,

    I had unprotected sex with sex worker on 17/10/17 and after 7 days I had hiv 1&2 test which is non reactive, than I had 4th generation test hiv1/2 & p24 combi (cmia) after 26 days & 55 days both are also nonreactive (index value is 0.09 & 0.10)
    1 – I just want to confirm if the p24 combo test i has done after 26 days is non reactive then it can be possibility that I have hiv.
    2 – Do I believe that p24 combi test after 26 days & 55 days is a conclusion that I don’t have hiv and I should be relax and don’t required more test.

    Please clear all my query as I am too much worried about the test conclusion result that are that accurate after 55 days.

    • Your latest test at 55 days is conclusive. No HIV.

      • So Dr. Can I go forward to my life and can make contact with my wife as we are planning for child.
        There will be no further problem to my wife after making sexual relationship with her, as is that fully clear that I don’t have hiv and no need for further test.
        Please reconfirm it so that I be relax and plan for kid.
        Waiting for your kind response.

        • Dr. Please reply on my last message, it’s imp understand for my family planning.

        • Dr. Tan, why are you not replying on my last message, pls reply it’s imp for both me and my wife, pls understand.

  20. Good evening doctor I got a hand job from a lady after the hand job I just see a small cut on the finger of the lady I don’t know it’s bleeding or not during the hand job now am really scared if the cut is bleeding and the blood got on my urethra or penile head any risk of HIV please doctor I need a HIV test or not???

  21. I had a female massage parlor girl insert her finger in my rectum massing my prostate. She did not use any protection. She may have hiv and bled in me. Since then have felt ill and now developed black tarry stool which we presume is ulcer. I tested with combo duo test at 20.5 days after exposure and was negative. How reliable is that result even with symptoms.

    • Your risk from this exposure is essentially zero. However, for conclusive HIV testing, I would recommend a repeat at 28 days or more post exposure. If you still have symptoms of concern, please visit us for a proper consult and assessment.

  22. Alejandro

    Hello Doctor,

    I am male from the US and my exposure was low risk I believe. Urethra came in contact with vaginal fluid through hand job she have after touching her vaginal fluids, so outside the body. Since then I have had 4th Gen Abbot Architect tests after 8, 21, 36, and 53 days of exposure. All 4 tests negative. I also had HIV PCR RNA on 36 day which was undetectable. Are these tests conclusive? I have had electric sensations and pain in fingertips/legs/toes for a month now and they won’t go away which adding to anxiety. Please help!

    • Your tests are conclusive and your initial risk is zero. If you have symptoms of concern, please have them assessed by a doctor.

      • Hello doc I had protected sex with a person status I don’t know of on October 6 2017 I seen the condom on him the whole time.One October 21 2017 I had unprotected sex ….November 30 I went got test they used the 4th generation test with reflex i had to wait over the weekend to get my results it was non reactive my thyroid was just low I’ve been living with herpes since 2009….on December 21 2017 I did a at home oraquick test which was negative!!But I’ve been having post nasal drip which I can’t get rid of with joint aches hear to there!I don’t know what I should do please help!Im convinced I done got hiv from these symptoms

        • Your tests are conclusive – no HIV. If you are still having anxiety, you should consider speaking to a counsellor/psychiatrist.

  23. Hello doctors, I’m from Brazil, and had a risk exposure a time ago,make a combo teste with 42 days negative, still with fear make another one with 62 days combo test negative, on january 12 will make 3 months

    1) my two tests are conclusive?

    2) sould I take another one with 90 days? Results can change?

    3) I’m still scare, sould Í try teraphy?

  24. I’m from India doc sir I had gone to 2015 one lady with sex but I’m not intercourse only pinis massage without condom and kiss her face and rub vegina area and once again I am I had gone 2017 December 15 same lady meet her same insedent 2015 two times pcr rna quality and quantity test was negative and cmia tests almost done 20 times all tests negative for hiv test 3month and 6 months can I hiv test need and what is window period for hiv test conclusive in India 2017

    • The risk from this exposure is zero. Stop testing.

      • Thanks doctor happy Merry Christmas and happy new year

      • Dear Dr Jonathan ,

        I was having HIV anxiety and your response on my 9 weeks non reactive result helped me to get rid of it . I would like to thank you for your constant support in this HIV forum . Wishing you a Happy new Year !

        Thanks & Best Regards,

  25. Hi doc,

    34th day test, HIV I/2 & Antigen and antibody screening, result non – reactive. Conclusive?

  26. Tq, doctor i got unprocter sex with sex worked 28day test negative means i no got hiv right?

  27. What is the hiv 1/2ag+ab p24 screen werten blot ? I got 28day test negative is that i got a restest at 3 month ?

  28. hai doc

    I already test 4generations 53day after risk(negative) and 93day 4generations/lab test (negative)…my question any case become positive the next test from doc experience?sorry doc my English bad.

  29. Hiv 1/2(ab+ag)p24 is that same with combo ,dua test?

  30. Hi,dr i have protected sex with a sex worker after 33day i have hiv 1/2 (ab+ag)p24 screen is no reactive is that mean i hiv free? P24 hiv(ab+ag) is that 4th generation?

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