HIV/AIDS Health Center

There are two major types of HIV tests — one that tests for antibodies to the virus and another that tests for antigens.

Antibodies form in the body as a result of an HIV infection. Antibodies usually take about 12 weeks to form but, in rare cases, can take up to a year. Blood tests for antibodies tend to be more accurate because antibody levels are often lower in saliva.

HIV antigens are proteins the HIV virus produces directly after it infects you. HIV antigen tests are usually accurate in a shorter amount of time than antigen tests — usually about three weeks. Antigen tests only examine the blood.

If you are diagnosed with HIV, you may undergo more tests to find out how advanced the virus is. These tests commonly include a T-cell test. T-cells are a type of white blood cell that HIV attacks. You may also undergo a viral load test to determine how much of the virus is in your blood or a drug resistance test to see whether the strain of HIV you have is resistant to medication.