An HIV test checks for HIV antibodies in the blood. If HIV antibodies are found, the test is considered positive.
Most doctors use two blood tests, called the ELISA and the Western blot assay. If the first ELISA is positive (meaning that HIV antibodies are found), the blood sample is tested again. If the second test is positive, the doctor will do a Western blot to be sure.
Most test facilities will have the ELISA test results in 2 to 4 days. Results of the Western blot take longer, 1 to 2 weeks. Rapid antibody tests are available that give results right away. But positive results of the rapid test need to be confirmed by the ELISA or Western blot test.
Even if HIV antibodies aren't found, you may need to be tested again, especially if you think you have been exposed. This is done to make sure that HIV antibodies don't appear at a later time. It can take as little as 2 weeks or as long as 6 months from the time you become infected with HIV for the antibodies to be found in your blood. Tests given at 6, 12, and 24 weeks can be done to be sure you aren't infected.
During this period, an infected person can still spread the infection even though his or her test was negative.
You can get HIV testing in most doctors? offices, public health clinics, hospitals, and Planned Parenthood clinics. You can also buy a home HIV test kit (saliva test) in a drugstore or by mail order. But be very careful to choose only a test that has been approved by the U.S. Food and Drug Administration (FDA). If a home test is positive, you'll need to see a doctor to have the result confirmed and to find out what to do next.