July 8, 2012
HIV testing tells you if you are infected with the Human Immunodeficiency Virus (HIV) which causes AIDS. Most of these tests look for "antibodies" to HIV. Antibodies are proteins produced by the immune system to fight a specific germ. Newer HIV tests look for signs that the virus itself is in the blood.
People who already know they are infected with HIV might get other "HIV" tests. These measure how quickly the virus is multiplying (a viral load test, see Fact Sheet 125) or the strength of your immune system (a CD4 count, see Fact Sheet 124).
In September 2006, the US Centers for Disease Control recommended routine HIV screening of people in healthcare settings. This should result in more general HIV testing in the US.
You can arrange for HIV testing at any Public Health office, or at your doctor's office. Test results are usually available within two weeks. In the US, call the National AIDS Hotline, (800) 342-2437.
The most common HIV test is a blood test. Newer tests can detect HIV antibodies in mouth fluid (not the same as saliva), a scraping from inside the cheek, or urine. "Rapid" HIV test results are available within 10 to 30 minutes after a sample is taken. In November 2010 the FDA approved the INSTI test, which gives results within 60 seconds. In 2012, the FDA approved the first true "in-home" HIV test. It uses a mouth swab and shows results in 20 to 40 minutes. A positive result on any HIV test should be confirmed with a second test at a health care facility.
Many people are infected with HIV but don't know it. You might not feel sick or have any health problems. But you can still pass HIV to other people. Anyone who is sexually active should get tested regularly for HIV.
If you are infected with HIV, it usually takes from three weeks to two months for your immune system to produce HIV antibodies. During this "window period you can test "negative for HIV even if you are infected. If you think you were exposed to HIV, you should wait for two months before being tested. You can also test right away and then again after two or three months. If you are infected, you can transmit HIV to others during the window period even if you test negative. In fact, during this period of early infection, you have the greatest chance of passing HIV infection to others.
About 5% of people take longer than two months to produce antibodies. Testing at 3 and 6 months after possible exposure will detect almost all HIV infections. However, there are no guarantees as to when an individual will produce enough antibodies to be detected by an HIV test. If you have any unexplained symptoms, talk with your health care provider and consider re-testing for HIV.
Viral load tests detect pieces of HIV genetic material. They show up before the immune system manufactures antibodies.
The viral load or nucleic acid tests are generally not used to see if someone has been infected with HIV because they are much more expensive than an antibody test. They also have a slightly higher error rate.
In 2010 the FDA approved a new blood test that detects both antibodies to HIV and HIV antigens (pieces of the virus.) This "fourth generation" test produces results faster than an antibody test.
A positive test result means that you have HIV antibodies, and are infected with HIV. This can be a very difficult time. Be sure to get information and help. See Fact Sheet 201, "How Do I Start?"
Testing positive does not mean that you have AIDS (See Fact Sheet 101, What is AIDS?). Many people who test positive stay healthy for several years, even if they don't start taking medication right away.
If you test negativesix months after you think you were exposed to HIV and if there is no chance you were exposed to HIV since then, you are not infected with HIV. Continue to protect yourself from HIV infection (See Fact Sheet 150, Stopping the Spread of HIV).
You can be tested anonymously in many places. You do not have to give your name when you are tested at a public health office, or when you receive the test results. You can be tested anonymously for HIV as many times as you want.
If you get a positive HIV test that is not anonymous, or if you get any medical services for HIV infection, your HIV infection may be reported to the Department of Health and counted in statistical reports.
Antibody test results for HIV are accurate more than 99.5% of the time. Before you get the results, the test has usually been done two or more times. The first test is called an "EIA" or "ELISA" test. Before a positive ELISA test result is reported, it is confirmed by another test called a "Western Blot. This is why home test kits cannot tell you if you have HIV infection. The sample you collect must be tested by a laboratory.
Some special cases can give false or unclear results:
Children born to HIV-positive mothers may have false positive antibody test results for several months because mothers pass many types of infection-fighting antibodies to their newborn children. Even if the children are not infected, they have HIV antibodies and will test positive for about 18 months. Other tests, such as a viral load test, must be used.
People who were recently infected may test negative during the window period if they get tested too soon after being infected with HIV.
Pregnant women may have false or unclear test results due to changes in their immune system.
In rare cases, HIV test results can be unclear of "indeterminate." Another blood sample is taken for additional testing.
HIV testing generally looks for HIV antibodies in the blood, or saliva or urine. The immune system produces these antibodies to fight HIV. It usually takes two to three months for them to show up. In rare cases, it can take longer than three months. During this "window period you may not test positive for HIV even if you are infected. Normal HIV tests don't work for newborn children of HIV-infected mothers.
In many places, you can get tested anonymously for HIV. Once you test positive and start to receive health care for HIV infection, your name may be reported to the Department of Health. These records are kept confidential.
A positive test result does not mean that you have AIDS. If you test positive, you should learn more about HIV and decide how to take care of your health.