The HIV test is designed to detect antibodies to HIV in your blood or saliva. Antibodies are "fighter cells" produced by your body when you have an infection. If you are infected with HIV, your body makes very specific antibodies to fight the infection. The HIV antibodies are different from antibodies for the flu, hepatitis, or other infections. If you have HIV antibodies, then you have been infected with HIV. (The only exception to this applies to infants born to HIV-infected mothers; infants can receive HIV antibodies from their infected mothers that stay in their system for as long as 18 months.)

The HIV test does not tell you if you have AIDS or how long you have been infected or how sick you might be. It just tells you that you are infected with the virus (see What are HIV/AIDS?).

The window period is the time it takes for your body to produce HIV antibodies after you have been exposed to HIV. In more than 99% of people, this period is between 2 and 12 weeks. In a very small number of people, the process takes up to 6 months.

The window period causes a lot of confusion. Here's an example: Let's say someone had unprotected sex on Saturday night. On Monday, he goes to get an HIV test. The test will almost certainly come back negative, even if he was infected with HIV on Saturday night, because his body has not yet had a chance to make antibodies. Even if he went for an HIV test 1 or 2 months later, he might still get a negative result even if he had been infected on that Saturday night; again, the reason is because he has not yet produced antibodies, which are what the HIV test is looking for.

If you are worried about something that happened that may have exposed you to HIV, you naturally will want to get tested as soon as possible. A good strategy would be to go back for a test 3 months after your possible exposure; the result you get after 3 months will be 99% certain. However, if you think you may have been exposed to HIV and are having symptoms of HIV infection, see a doctor right away. The doctor may be able to perform a different kind of test called a Polymerase Chain Reaction (commonly called "PCR") test that can detect actual virus (versus the antibodies to the virus) in the blood. If you think you may have been exposed to HIV recently (regardless of whether you have symptoms), talk to a counselor or health care provider about when you should be tested.

The testing process could vary a lot depending on where you live and where you get tested.

	Testing sites are either confidential or anonymous. At anonymous sites, you are given an identification number so that you do not have to give your name. This is a good option for someone who is concerned about others finding out about their decision to get tested because only you can match your number with your test result.

	Some testing sites require you to make an appointment, others offer hours when you can drop in to get tested. If it is a drop-in clinic, clients are seen in order of arrival; therefore, you may have to wait for a little while. For appointment clinics, you can call the testing site to schedule a time for counseling and testing.

	Most sites use a client questionnaire to collect some information about you like your ethnicity, sexual orientation, sexual activity, substance use, and whether you have ever had an HIV test before.

	Before the test, you will talk with a counselor who explains the testing process, answers your questions about HIV, and addresses any other concerns you have. The counselor can also answer questions and offer advice about reducing your risk for HIV.

Many testing sites use a small blood sample to test for HIV. Many other testing sites use a test called OraSure. With this test, a probe that looks like a toothbrush sits in your mouth between your cheek and gums for about 4 minutes. Results from either type of test usually take one to two weeks. There is a new type of test called a "rapid test" where you can receive the results in less than 30 minutes. In the rapid test, clinic staff prick your finger with a needle and take a few drops of your blood. Whether you receive counseling with the rapid test depends a lot on where the test is given. If you are offered the test in an emergency room of a hospital, for instance, the staff may not have the time or training to give you much counseling.

	At your return appointment, you sit with a counselor who gives you your results and answers questions. If your test results are positive, they will give you referrals for physical and mental health care, housing, and other services you may need. If your results are negative, they can discuss ways to protect yourself against HIV in the future.

If you take the test from your regular clinic or doctor's office, you may not receive the same amount of counseling as from a special HIV test site. However, you may be able to make an appointment at a more convenient time and not have to wait. You may want to weigh your comfort level with your doctor or regular clinic against the more specialized counseling and referrals you would receive at a special HIV test site. You may also want to consider the availability of anonymous testing at a regular clinic or doctor's office.

See Beyond Basics: What kinds of HIV screening tests are available in the United States? for more information.