The HIV test
A test can tell if you have become infected with HIV. If you have, this is described as being HIV positive. There are two different types of tests which can detect HIV.
One type looks for the antibodies the immune system produces to fight HIV infection. Another type looks for the HIV itself (sometimes called an antigen test, or a p24 test). Most clinics use a test which includes both of these types - an antibody test and an antigen test. This means that HIV can be found sooner after infection than it would be by using an antibody test on its own. Using this test, the majority of people who have HIV can be diagnosed within one month of being infected.
For a person whose last possible exposure to HIV was at least one month ago, a negative result should be very reassuring. Nonetheless, for a very small number of people, it can take up to three months for the test to give an accurate result.