Most HIV tests (at clinics, doctor's offices, and testing sites) are designed to detect the antibodies that the body produces to fight HIV once infection has occurred, but do not test for the virus itself.  It can take some time for the immune system to produce enough antibodies for these tests to be able to detect them, and this time period can vary from person to person.  Most people will develop detectable antibodies within three months, but it can take longer, including up to six months in some cases. This time period is known as the "window period", when an individual may be infected with HIV, but may not yet test positive. There are several kinds of HIV tests available in the U.S. The main types of tests are:

Conventional blood test: A blood sample is drawn by a health care provider and tested at a lab. Results are generally available within a few days to two weeks.

Conventional oral fluid test: a health care provider, who swabs the inside of the mouth, collects an oral fluid sample. The sample is tested at a lab. OraSure is the only Food and Drug Administration (FDA)-approved HIV oral fluid test. Results are generally available within a few days to two weeks.

Rapid tests: Rapid HIV tests are performed at testing sites and can provide results in as little as 20 minutes, depending on the test. If a rapid test is negative, no further testing is needed. If a rapid test is positive, it must be confirmed with a more specific test performed in a lab. Four rapid tests recently approved by the FDA are commercially available. Some require a finger prick, others a blood draw from the arm, and one can use oral fluid.

Home Tests: A home HIV test first came onto the market in 1997. HomeAccess, the only home HIV test currently approved by the FDA, may be purchased from many drug stores and online. An individual pricks their finger with a special device, places drops of blood on a specially treated card, and mails the card to a lab for testing. Using an identification number printed on the card, they phone for test results and may also receive counseling and referral by phone. Results can be obtained in as little as three days.

Urine Test: A urine sample is collected by a health care provider and tested at a lab. Calypte is the only FDA-approved urine HIV test. Results are generally available within a few days to two weeks.