Hie, I am a 20 year old lad who was very foolish to engage in a very risky activity with a girl I did not know very well. I went for an HIV test after 3 months from the posible day of exposure. It came back negative. However I am really worried even now, since I see you mention cases of people testing positive between 3 and 6 months. My Question is what determines the window period? Could body weight have anything to do with time from exposure to generation of antibodies? I weigh 215 pounds. Joram Mubwandarikwa

Joram,

Thank you for your question.

It is true that people can take up to 6 months to show positive on the test. But many people can show positive before 6 months. More specifically:

The AVERAGE period of time that an infected person will show positive on the test is 25 days. This is an average, so not all people will test positive by this point in time.

The USUAL period of time that an infected person will show positive on the test is 3 months. This means that most (but not all) infected people will show positive on the test by this time.

The MAXIMUM period of time that an infected person will show positive on the test is 6 months. By this point in time, more than 99% of infected persons will show positive on the test. This is as accurate as any test in medicine could ever be.

So in your case, if you have tested negative at 3 months, we can say that you're probably not infected. There is still a chance that you can have the virus, but it has not yet shown positive on the test. But since most people who are infected do show positive by 3 months, things so far appear to look good for you. But a 6 month test will be the most accurate test.

I have never seen body weight as a factor in when a person produces antibodies. Some people naturally produce antibodies faster than other people. All of our bodies are different from one another, and they all respond differently from one another. But I've never heard of a persons weight having anything to do with the window period. Also, generally speaking, a person with other medical problems, especially problems relating with the immune system, may take longer than the majority of the population, to show positive on the test.

If you have any further questions, please feel free to call the Centers for Disease Control at 1.800.232.4636 (Nationwide). Rick Sowadsky MSPH CDS