What is an HIV test?
An HIV test checks a sample of your blood to see whether you are infected with HIV (human immunodeficiency virus). HIV is a virus that destroys certain cells in your immune system. These cells protect your body against diseases from germs, such as bacteria and viruses, and fungi. If you lose too many immune cells, your body will have trouble fighting off infections and other diseases.
HIV is spread through contact with blood and other body fluids from a person who has an HIV infection. This usually happens during sex or when sharing needles or other items used to inject drugs.
HIV is the virus that causes AIDS (acquired immunodeficiency syndrome). AIDS is the final, most serious stage of an HIV infection. Without treatment, HIV gradually destroys your immune system, which leads to AIDS. With AIDS, your body has trouble fighting off infections from germs that usually don’t cause problems in healthy people. These are called opportunistic infections, and they can become life-threatening. AIDS increases your risk of developing certain cancers, too.
Most people with HIV don’t have AIDS. If you have HIV and you take HIV medicines as prescribed, you may never get AIDS. Getting tested for HIV helps catch the virus early so you can start treatment, stay healthy, and avoid spreading HIV.
If you think you were exposed to HIV, talk with your healthcare provider right away about emergency treatment, called PEP (post-exposure prophylaxis). PEP may prevent an HIV infection if it is started within three days after possible exposure. The sooner you start, the better. You will need to have HIV tests during and after taking PEP.
There are three main types of HIV tests. They are all very accurate, but no test can find HIV in your body immediately after you’re infected. That’s because it can take weeks until the signs of HIV in your body increase enough to show up on a test. The time between infection and when a test can find HIV depends on your body’s response to HIV and the type of test you have:
HIV antibody tests look for HIV antibodies in your blood, saliva (spit), or urine (pee). HIV antibodies are disease-fighting proteins that your immune system makes when you have an HIV infection. Some people make antibodies faster than others. An antibody test may find HIV antibodies as early as 23 days after infection, but it may take as long as 90 days before your body makes enough antibodies to show up on this test.
Antibody tests can be done in different ways:
- Lab tests use a blood sample taken from a vein. In general, lab tests can find antibodies sooner after infection than other HIV antibody tests. Test results are usually ready a few days after your blood sample is taken.
- Rapid tests use blood from your finger, saliva, or urine. They provide results in about 30 minutes.
- At-home tests include rapid self-test kits with everything you need to collect and test a sample of saliva on your own. With mail-in tests, you collect a drop of blood from your finger to send to a lab for testing.
HIV antibody/antigen tests are the most commonly used HIV tests. They look for HIV antibodies and antigens in your blood. An antigen is the part of the HIV virus that triggers your immune system to fight the infection. After an HIV exposure, antigens will show up in your blood sooner than antibodies:
- Lab tests that use a blood sample from a vein can find an HIV infection as soon as 18 to 45 days after you were infected.
- Rapid tests use a drop of blood from your finger. This test can find HIV infections starting between 18 days to 90 days after you were infected.
- At-home tests, or mail-in tests, allow you to collect blood from your finger at home to send to a lab for testing. Like rapid tests, these tests can start finding HIV 18 to 90 days after infection.
NAT tests (nucleic acid tests) look for HIV in a sample of your blood taken from a vein and tested in a lab. These tests may also be called “viral load tests.” They can usually find an HIV infection as soon as 10 to 33 days after infection. But they are mostly used for monitoring HIV treatment and not for routine screening because they are expensive. Ask your provider about having a NAT test as soon as possible if you:
- May have been exposed to HIV and have symptoms, such as:
- Flu-like symptoms, including fever, chills, and aches.
- Extreme fatigue
- Swollen lymph nodes (in your neck, groin, or armpit)
- Sores in your mouth
- Know you were exposed to HIV or were very likely exposed.
Other names: HIV antibody/antigen tests, HIV-1 and HIV-2 antibody and antigen evaluation, HIV test, human immunodeficiency virus antibody test, type 1, HIV p24 antigen test
What is it used for?
An HIV screening test is used to find out if you have been infected with HIV. It may be done as a routine test or after a possible exposure to find out if you were infected with HIV.
If HIV is found early, you can take medicines to protect your health, so you don’t get AIDS. And medicines can help you avoid spreading HIV to others.
Why do I need an HIV test?
The Centers for Disease Control and Prevention (CDC) recommends that everyone between the ages of 13 and 64 get tested for HIV at least once as part of routine health care.
You may need to be tested more than once if you have a higher risk for infection.
If your last HIV test was more than a year ago, you should get tested as soon as possible if you have:
- Had vaginal or anal sex with someone who has HIV (HIV positive) or whose HIV status you don’t know.
- Injected drugs and shared needles, syringes, or other drug items with other people
- Exchanged sex for money or drugs.
- Had a sexually transmitted disease (STD), such as syphilis.
- Had sex with anyone who has done anything listed above.
If you regularly do any of the things on the above list, you should be tested for HIV at least once every year. Certain people, including men who have sex with men (MSM), may benefit from being tested more often, depending on their risk. Ask your provider how often you should be tested.
If you are pregnant, your doctor may order an HIV test. That’s because HIV can be passed to the baby during pregnancy and birth, and through breast milk. There are medicines you can take during pregnancy and delivery that greatly reduce your risk of spreading HIV to your baby.
What happens during an HIV test?
There are many places to get tested for HIV, including at your doctor’s office, health clinics, testing programs in your community, and at home. If you go somewhere for your test, a staff person or counselor will explain what type of sample will be taken and how. If you do a test at home, be sure to follow all the instructions that come with your test kit.
For blood from a vein, a healthcare professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
For blood from a finger, a healthcare professional will use a special tool (lancet) to prick your finger and collect a sample of blood. If you are collecting your own blood sample to send to a lab, follow the instructions that come with your collection kit.
For a saliva sample, a healthcare professional will wipe a special swab along your gums. If you are doing an at-home test, you will do this yourself according to the instructions.
Will I need to do anything to prepare for the test?
You don’t need any special preparations for an HIV test. If you are getting tested in a health clinic or community program, a counselor may talk with you about your risk for HIV. So, you may want to write down any questions you have ahead of time.
Are there any risks to the test?
There is very little risk to having any HIV screening test. If you have blood taken from a vein, you may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
What do the results mean?
A negative test result means that no signs of an HIV infection were found in your sample. But that doesn’t always mean that you don’t have HIV. You could have an HIV infection, but it’s too soon for the test to tell and you made need another test later. Your provider or an HIV counselor can explain your test result and let you know if you need another test.
In general, if you have a negative result on a rapid test or an at-home test and a possible HIV exposure that was:
90 days ago, or longer, you can be confident that you don’t have HIV
Less than 90 days ago, you will likely need another test later to check for HIV again.
A positive test result means that signs of an HIV infection were found in your sample. You will need a follow-up test to confirm an HIV diagnosis unless you had a NAT test.
If you used an at-home test, see your provider for follow-up testing.
If you had your test at a medical office or community program, the testing site will arrange your follow-up test.
If your follow-up test is also positive, it means you have HIV. It’s important to start medicines called antiretroviral therapy (ART) right away, even if you’re still healthy. ART can’t cure HIV, but it may lower the amount of virus in your blood so much that a test can’t find it. If you’re living with HIV, it’s important to see your provider regularly for tests to check how your treatment is working.
Is there anything else I need to know about HIV screening?
HIV testing can be anonymous. That means you do not have to give your name when you take an HIV test. Instead, you’ll receive a number. To get your test results, you’ll give the number instead of your name.
Source: MedlinePlus, National Library of Medicine
MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.