Antibody tests (serology tests) look for antibodies in your blood. Antibodies are proteins your immune system makes to fight infection. These tests help your provider confirm a diagnosis of a wide range of diseases, disorders and infections, including COVID-19. Talk to your provider about whether you need an antibody test.
An antibody test looks for antibodies in your blood. Antibodies are proteins your body makes to fight infection. Your immune system creates unique antibodies to respond to different unknown substances such as viruses, bacteria and allergens (tiny particles that cause allergies). Providers also call this test a serology test.
Healthcare providers use antibody tests to tell if you’ve had an infection or if you’ve been exposed to a specific virus. A more recent example of this is the antibody test for SARS-CoV-2 (the virus that causes COVID-19). If you test positive for COVID-19 antibodies, that means you’ve been exposed to that virus and your body created antibodies to fight it. Your immune system also develops COVID-19 antibodies after you receive the COVID-19 vaccine.
After a vaccination, infection, or exposure to infectious agents, it can take up to several weeks for your immune system to make antibodies. Antibody tests are not the same as diagnostic tests that check for an active (current) infection. These tests do not detect the infectious agent itself. They evaluate your body’s response to the virus.
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You may need a COVID-19 antibody test if you:
Providers also use antibody tests to evaluate you or your child for allergies. The tests can tell if your immune system created antibodies in response to various allergens. Providers call the response an allergic reaction. But some of these tests (especially antibody tests for food allergies) can produce a false-positive result. That means the results might be positive for antibodies, but you may not actually be allergic.
A healthcare provider performs this test. You get the test at your doctor’s office, a laboratory or a special clinic.
Different serology tests detect different antibodies. Your body creates five main types of antibodies:
Consider the COVID-19 antibody test as an example of how the process works:
Most COVID-19 antibody tests look for IgM and IgG antibodies. Your body usually produces IgM antibodies first, as soon as you’re exposed to a virus like SARS-CoV-2. These antibodies fade away sooner than others and may not be detectable for very long.
IgG and IgA antibodies usually appear about a week to 10 days after you were exposed to the virus. Since IgG antibodies stay in your body longer, an antibody test may detect these antibodies for months or even years after a COVID-19 infection.
COVID-19 vaccines (such as the mRNA vaccine) teach your body how to create antibodies that fight the virus. So, you might test positive for COVID-19 antibodies if you get an antibody test after your vaccine. But your results will depend on several factors, including when you get the test and what type of antibody test you get. Different antibody tests check for different types of antibodies.
Your provider takes a sample of your blood and sends it to a lab. The lab tests your blood for antibodies. It also measures the levels of specific types of antibodies.
There aren’t any special preparations needed for this type of test. You may want to wear a short-sleeved shirt to make it easier for your provider to access a vein in your arm.
Your provider cleans the skin on your arm. They insert a needle into a vein. You will feel a pinch when the needle goes in, but it usually doesn’t hurt. Your provider removes a sample of your blood through the needle and collects it in a tube. Then they place a bandage on your arm.
Instead of using your arm, your provider may prick the tip of your finger to draw blood. Your provider will tell you if it’s best to use your arm or your finger for the blood draw.
Your arm may be a little sore for a few hours after the test. You’ll have a piece of gauze and a bandage on your arm, which you can remove after a few hours. A little bruise may appear where your provider inserted the needle.
You may get your results the same day. Or, your provider might send your blood sample away to a lab, so results might not be ready for a few days. Ask your provider when you can expect results.
A positive test result means there are antibodies in your blood, which can include COVID-19 antibodies. In the case of a COVID-19 antibody test, the antibodies could be the result of your body’s response to the COVID-19 vaccine. Or the presence of antibodies could mean you were exposed to COVID-19 in the past and your body developed antibodies to fight the virus.
Typically, the more severe the infection, the higher the level of antibodies. But even people who had mild symptoms (or no symptoms at all) can test positive for antibodies.
Antibodies can protect you from getting infected by the same germ in the future. But the length of time that protection lasts depends on several factors, including the type of virus or bacteria. That’s why providers don’t use antibody tests to check for immunity to COVID-19.
A negative test result could mean:
Talk to your provider if you have questions about your test results. If you develop symptoms of COVID-19 or continue to have symptoms from the infection after a couple of weeks, call your provider right away.
A note from Cleveland Clinic
Antibody tests help your provider confirm a diagnosis of a wide range of allergies and diseases, including COVID-19. They also help your provider evaluate your immune system’s response to viruses and bacteria after you’ve been exposed to them. If you have questions about the results of your antibody test, call your provider. In some cases, you may need a second antibody test to confirm your results. See your provider right away if you develop symptoms of COVID-19 or if you continue to have symptoms after the infection.
Last reviewed by a Cleveland Clinic medical professional on 05/17/2022.
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