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!

HIV – Understanding the Window Period

Asian Geographic article on HIV

Asian Geographic article on HIVThe HIV window periodoften is the cause of a lot of confusion.

There is a lot of information on the web throwing up numbers like 3 months, 6 months even 1 year. So what exactly if the HIV window period?

To better understand this, let us take a step back in time to when HIV was first discovered. At the same time, learn a little about how our immune system works.

The HIV virus was discovered in 1983. Prior to that, it was not known what was causing the disease known as AIDS that was ravaging certain communities in the world.

After scientists discovered the existence of the HIV virus, they had to find a way to determine if a person has this virus in his body or not.

The ELISA Test and Our Immune System

In 1985, they developed a test called ELISAwhich is based on a very basic principle of how our immune systems work.

When our body is attacked by a virus, it will produce anti-bodies to fight the virus. Anti-bodies are unique. The anti-bodies used to fight HIV would be completely different to the ones used to fight dengue, for example, or any other virus.

So finding HIV anti-bodies in the body is indirect evidence that there is HIV virus in the body too. The ELISA test does exactly that. It tests for the presence of HIV anti-bodies. HIV rash

Imagine each virus infection is a fire that starts in the body. Each of these fires produces a uniquely colored smoke. When we see a particular colored smoke, we assume that there is that particular type of fire burning away. The ELISA tests for HIV colored smoke but does not detect the fire itself.

But there was one big problem. It sometimes takes the body a long time before the body produces enough anti-bodies to be detected by the ELISA test. In other words, the fire has to burn for a long time before it produces enough smoke that can be detected by ELISA.

This period when a person is infected with HIV and the ELISA test is unable to pick it up (the period when the fire is burning but there is no smoke) is called the window period.

This was correctly recognized to be a very important finding and rightly so because a person infected with HIV within the window period can get tested and be told he does NOThave HIV. He will then not take steps to protect himself and the people around him thus increasing the risk of spreading the disease.

Different Types of HIV Tests

Click on the picture for the latest information on the HIV testing Window Period

Click on the picture for the latest information on the HIV testing Window Period

Click here for HIV Testing FAQ

Scientist has ever since been working on improving and coming up with new and better testing techniques and technology. There are now multiple different tests for HIV including ELISA, ECLIA, CMIARapid HIV Tests, Western Blot, RNA PCR, DNA PCRand P24 Combo Tests.There are also multiple different manufacturers of each test. All of these tests have their own rates of accuracy, window periods and applications in the management of HIV. To make things even more confusing, there are also tests for indirect evidence of HIV infection like CD4 cell count and CD4 CD8 cell ratio.

So when you read somewhere or someone tells you that the window period for HIV is X number of months, your next logical question should be ‘by using which test?’ – HIV Test Singapore

To know which test done when has what accuracy requires a lot of professional knowledge. This information is also constantly changing as more and more research information is published. There are also other considerations such as waiting time, anonymity, costs etc

It is still best to speak to Our Doctors who are certified and trained in HIV counseling and testing to find out which test is most appropriate for you. Anonymous HIV Testing

Click here for Updates on the HIV testing Window Period

One thing remains constant. If you are at any risk of HIV at all, no matter how minute, you MUSTget tested. But as for which test to do and when to test, it is still best to speak to a medical professional trained in HIV matters.

Click here to learn about the Different Generations of ELISA

The HIV Window Period and Test Accuracy

HIV PEP Post Exposure Prophylaxis


Click here for Info on STD Symptoms in Men

Click here for Info on STD Symptoms in Women
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 .


Need more advice?

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

Singapore Branches


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.



  1. Hello i had a HIV RNA test and my result was ” not detected” 18 days after my exposure …is it conclusive??thanyou for your reply doctors ..Godbless

    • I would consider it essentially conclusive. Although by strict guidelines RNA testing is not recommended as screening, and you would be advised to do a 4th generation combo test at 28 days of later.

      • Hello dear please help me. I have handjob with hiv positive person she has cut on her hand i have also cut on my penis please tell me i am on risk. I have done hiv combo test after 32 days 84 day and 120 days all came negative. Please tell i nead futher testing.

  2. Am circumcised and had protected sex with a woman but later removed the condom and ejaculated in her a min after entering her. After 3 days i tested her and the results were positive and i came out negative. After worrying and researching about HIV i got so worried and scared and couldn’t sleep that night. the following day i started experiencing the symptoms. Had a mild flu,mild headache though maybe just 1min and am fine. Started feeling weak and lost a bit of appetite. Yesterday was the 12th day and i felt like i was developing sores in my mouth,i took nystatin oral n today am better, just feeling them a bit. I also had a sweaty night. My temperature is normal at 36.7c. Am stil scared such that i spend not of my time researching on the internet about HIV. What are the chances of me being infected and can symptoms start at 4 days after exposure? Am so so scared. And are the symptoms usually mild or what? Due to fear i did a test with SD biolin 3.0 it came out negative though i know this is very far from being conclusive.

    • It is highly unlikely to develop any symptoms like that within the first 1-2 weeks. Please perform the appropriate testing after the window period for conclusive results.

  3. Dwi Nanda Listya Utama

    I was wondering if you guys could inform me on what the hiv ars rash looks like. I’m asking because I have these small red itchy bumps on my right arm. It starts with one small bump at my arm and goes down to the middle and the left arm about 2 days after the first one. It’s like 12 of them, not grouped together but it located in different areas included two spot in my thigh. It’s really itchy so I’ve been putting itch powder and cream on them.

    Thanks in advance for all of your help.

    • There is no typical description of the rash – it can vary a lot. If you are concerned, please do visit us for a proper evaluation and testing if required.

  4. Hi sir. I am sex with a hiv positive girl. Single exposer but my test result are all negative. Ofter 15 months hiv rna pcr qualitative, hiv alere combo, western blot, elisa,tridot all are negative. But I cannot accept my result. I am dedaly worried pls. My test result ofter 15 months today elisa hiv, hbsag ,hcv, vdrl all are negative. Pls clarify me sir any further test needed. I am 100% negative or not.
    One doctor told me hiv ofter 5 &6 years become positive it is true….

  5. Doctor,
    Is window period of 4th gen test same for both hiv 1 and hiv 2.as i understand p24 antigen is only present in case of hiv 1.does my 55 day non reactive result also cover hiv 2?please tell.thank you in advance.

  6. Good day doctors!

    On 6 Jan wee hours i visited a massage parlour in JB for hand job service. During this transition, I did fingered her. Upon ending, she used a wet tissue to wipe my finger and then proceed with the same contaminated tissue to wipe my penis which I then proceed to the bath room in less than a min to clean off myself.

    I am worried with this exposure even though hiv risk is low. I took the 4th gen combo test on 26 Jan noon time which came out to be neg. Is this conclusive at day 20 to spot ag? Do i need a retest @ day 28? Also flu like symptoms from 20th Jan till today.

    Lastly, I would like to visit your clinic for syphilis and herpes test due to the above exposure even though no symptom of std in me.

    Thank you for your time!

    • I would consider your exposure risk to be essentially zero. The test is not considered conclusive until 28 days post-exposure (assuming an actual risk exposure). Please visit us for a proper consult and testing as appropriate. We do perform syphilis and herpes testing as well.

  7. The INSTI® HIV Self Test claimes to be potentially effective at 21-22 days (but not conclusive untill 3 months)

    Is there any data on how effective it is at 21-22days. I took a INSTI® HIV Self Test at 30 days post exposure that came back negative.

    I will follow up with additional tests I just want to have some idea how effective it is at this stage?

    thank you

    • I am not able to comment on home testing kits. Please visit a health care facility for proper testing at the appropriate time.

  8. daily ur reply all the person questions y not for me.
    I am waiting your replay pls sir……
    Thank you advance…….

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

  10. Dear Sir,
    I had unprotected vaginal sex with a woman. Later on 8 months I found out she had HIV.
    1).What are the chances a single exposure hiv transmission.2).ofter 8 months hiv westren blot negative.3).ofter 1 year hiv elisa test also negative.
    4).ofter 1 year hiv,hcv,hbsag,tpha,vdrl antibodies test are all negative.5).Does it mean I can forget about it and go on with my life?6).iam move on my wife with out condom?
    iam fully worried iam infected with hiv or not. pls iam fully confused clarify me one by one pls sir…
    i hope your clarify my confusion….

    Thank you….. in advance ……….

  11. Hi,dr I have protected sex with a sex worker after 33day i have hiv 1/2antibody/antigen p24 test is no reactive is that mean I am hiv free? The test is call western blot is that 4th generation?

  12. Hi,doctor hiv 1/2 antibody&antigen p24 is that 4th generation? And is that if I tset negative that mean I hiv free ?or need to retest again?

  13. Dear dr
    If I want check std and hiv need how long window period and the cost is how much?after sex with sex worker I have sex with my wife with condom can transmission to my wife?

  14. Dear dr
    I have protected sex with a sex worked about 15 min halfway the girl give me unprotected hand job and carry on with condom sex
    Now what can I do dr
    Can i have protected sex with my wife? At malaysian eclia is 3th generation or 4th generation?

Thank you for your submission.

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