University of California, San Francisco Logo

University of California, San Francisco | About UCSF | Search UCSF | UCSF Medical Center

Home > Public/Patient > Getting Tested > Testing for HIV
What happens when you get tested for HIV?
What is the test looking for?

The HIV test is designed to detect antibodies to HIV in your blood or saliva. Antibodies are proteins produced by your body when you have an infection and they help fight 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 indicate whether you have AIDS, how long you have been infected, or how sick you might be. It just indicates whether you are infected with the virus (see What are HIV/AIDS?).

The window period

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 97% of people, this period lasts 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 a standard antibody-based 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. There are HIV tests that look for the HIV virus itself rather than the antibody, and they can detect HIV infection earlier during the window period. Examples of these tests are an HIV PCR that detects the virus, and fourth-generation HIV tests that detect both HIV antibody and the p24 antigen, which is produced by the HIV virus.

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 provider right away. The provider may be able to perform a one of the tests that detect the virus directly. 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.

Testing process in the United States

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

Special testing sites
Testing sites are either confidential or anonymous. At anonymous sites, you are given an identification number so that you do not have to provide your name. This is a good option if you are concerned about others finding out about your 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, such as your ethnicity, sexual orientation, sexual activity, and substance use, and whether you have ever had an HIV test before.
Before the test, you may 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 of HIV. However, counseling is not mandatory for HIV testing; whether you get counseling may depend on the site where you are tested.
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 1 to 2 weeks. There is a rapid HIV test where you can receive the results in less than 30 minutes. For the rapid test, a clinic staff member will 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 may meet with a counselor who gives you your results and answers questions. If your test results are positive, the clinic will give you referrals for physical and mental health care, housing, and other services you may need. If your results are negative, the clinic staff can discuss ways to protect yourself against HIV in the future.
Regular clinic or doctor's office

If you take the test from your regular clinic or doctor's office, you may not receive the same amount of counseling as you would 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.

Learn More
Beyond Basics: What kinds of HIV screening tests are available in the United States?
I just tested positive for HIV -- now what?
I just tested negative for HIV -- now what?
National HIV Testing Resources
International Testing Resources
Locate testing sites and clinics around the world
AIDS organizations around the globe