Does this test have other names?

HIV test; human immunodeficiency virus antibody test, type 1, HIV p24 antigen

What is this test?

The test looks for HIV-1 antibodies in your blood.

Your body makes these antibodies when you have been exposed to HIV, the virus that causes AIDS.

All tests for HIV antibodies will look for HIV-1, which is more common than HIV-2 in the U.S. Combination tests have been developed to find HIV antibodies and HIV antigens called p24 antigens. The HIV antibody test advised by the CDC is the HIV-1/2 antigen/antibody combination immunoassay test.

If you test positive for HIV, the CDC advises the following follow-up tests:

• HIV-1/HIV-2 antibody differentiation immunoassay. This test is to confirm HIV and find out if you have HIV-1 or HIV-2.

• HIV-1 NAT (nucleic acid test). You will need this test to confirm the HIV-1 infection if you test positive on the first antigen/antibody combination immunoassay test and negative or undetermined on the antibody differentiation immunoassay.

Other follow-up tests, such as ELISA (enzyme-linked immunosorbent assay) and Western blot, may still be used. But they are not as common as they used to be.

Why do I need this test?

You may need this test if you have symptoms of an HIV-1 infection. Early symptoms are flu-like and include:

• Fever

• Cough

• Sore throat

• Rash

• Runny or stuffy nose

• Muscle and joint aches

• Diarrhea

• Headaches

You may also have this test if you've had unprotected sex and want to find out if you are HIV-positive. Testing is important to protect yourself and others, since you can be infected with the virus even if you don't feel sick. Men who have sex with men should be tested every 3 to 6 months. 

This test may also be done if you:

• Have shared needles to inject drugs. Needle-sharing has been linked with the spread of HIV infections.

• Are diagnosed with a different sexually transmitted infection (STI). This is because STIs generally suggest the possibility of high-risk behavior.

• Are pregnant. Pregnant women should be tested with each pregnancy, even if the testing was negative with earlier pregnancies.

• Are a healthcare worker who has been stuck by a contaminated needle or device. You should be checked at the time of the exposure and over the next 4 to 6 months.

What other tests might I have along with this test?

Your provider may also order viral load testing if they believe you have an acute HIV infection.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

If you test positive for HIV on this test, you will need one of the follow-up tests to confirm that you have an HIV infection.

Depending on your results, your healthcare provider may suggest that you speak with an HIV counselor.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect my test results?

Timing is important. It takes time for your body to make antibodies after you are exposed to a virus like HIV. Taking the test too soon after exposure can give a false negative. Most people will make antibodies 3 to 12 weeks after being infected

How do I get ready for this test?

You don't need to prepare for this test. Tell your healthcare provider about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.