What is an HIV test?
The HIV test determines whether you have been infected with HIV--the virus that causes AIDS.
When you get infected with HIV, the HIV virus replicates itself and spreads through the body, and your body produces cells and particles (antibodies) to fight the virus.
There are different types of HIV tests, some that can detect HIV itself (HIV antigen or viral load tests), and some that can detect antibodies to HIV in your body. If you have either HIV antigens or HIV antibodies (and this is confirmed by a second test), then you have been infected with HIV. The HIV test does not tell you if you have AIDS, how long you have been infected, or how sick you might be--for this you need other kinds of tests.
Using newer HIV testing methods, it is possible to identify most cases of HIV 2-3 weeks after infection. For more information, see Getting Tested for HIV/AIDS: Entire Lesson.