Testing for COVID-19

Two kinds of tests are available for COVID-19: diagnostic tests and antibody blood tests. Diagnostic tests check samples from your respiratory system (such as swabs of the inside of the nose) to tell you if you currently have an infection with SARS-CoV-2, the virus that causes COVID-19. Antibody blood tests, also called serologic tests, check your blood for antibodies that would show if you have had a previous infection. Antibodies are proteins that help fight off germs. A serologic test may not be able to show if you have a current infection, because it can take 1 to 3 weeks to make antibodies after symptoms occur.

We do not know yet if having antibodies to SARS-CoV-2 can protect someone from getting infected with that virus again, or how long that protection might last. Scientists are doing studies to answer those questions.

If you test positive or negative for COVID-19, no matter the type of test, you still should take preventive measures to protect yourself and others.

Diagnostic Testing

Diagnostic tests can find the virus that causes COVID-19 in samples taken from your respiratory system, such as swabs of the inside of your nose. Some tests are point-of-care tests, meaning results may be available at the testing site in less than an hour. Other tests must be sent to a laboratory to analyze, a process that takes 1-2 days once received by the lab.

How to decide if you should get a diagnostic test

Not everyone needs to be tested for COVID-19. Here is some information that might help you make decisions about getting a diagnostic test.

• Most people have mild illness and can recover at home without medical care. They may not need to be tested.
• At this time, there is no treatment specifically approved for people who have COVID-19.

CDC has guidance for who should be tested, but decisions about testing are made by state and local health departments or i healthcare providers.

How to get a diagnostic test

COVID-19 testing differs by location. If you have symptoms of COVID-19 and want to get tested, call your healthcare provider first. You can also visit your state or localexternal icon health department’s website to look for the latest local information on testing. Although supplies of tests are increasing, it may still be difficult to find a place to get tested.

In late April, the U.S. Food and Drug Administration (FDA) authorized a diagnostic test that lets you collect a respiratory sample at home. However, you will still need to send your sample – a swab of the inside of your nose – to a laboratory for analysis. The home collection kitsexternal icon will be available through healthcare providers in most states in coming weeks.

What to do after a diagnostic test

To get your test result, please check with the group that performed your test, such as your healthcare provider or your health department. Check the CDC website to locate your health department information. How long it will take to get your test results back depends on the test used.

• If you test positive for COVID-19, know what protective steps to take If You Are Sick or Caring for Someone.
• If you test negative for COVID-19, you probably were not infected at the time your sample was collected. However, that does not mean you will not get sick. It is possible that you were very early in your infection when your sample was collected and that you could test positive later. Or you could be exposed later and then develop illness. In other words, a negative test result does not mean you won’t get sick later. Know How to Protect Yourself and Others.

Additional information:

CDC: Frequently Asked Questions on Symptoms & Testing
U.S. Food and Drug Administration FAQs on Diagnostic Testing for SARS-CoV-2external icon

Serologic (Antibody) Testing

Antibody blood tests, also called serologic tests, check your blood by looking for antibodies, which show if you had a previous infection with the virus. Depending on when someone was infected and the timing of the test, the test may not find antibodies in someone with a current COVID-19 infection. Antibodies are proteins that help fight off germs. Serologic tests should not be used as the only way to diagnose someone as being currently sick with COVID-19.
Serologic tests are slowly becoming available through healthcare providers.

How to get a serologic test

Check with your healthcare provider to see if they offer serologic (antibody) tests.

• If you test positive:
  • A positive test result shows you have antibodies that likely resulted from an infection with SARS-CoV-2, or possibly a related coronavirus.
  • It’s unclear if those antibodies can provide protection (immunity) against getting infected again. This means that we do not know at this time if antibodies make you immune to the virus.
  • If you have no symptoms, you likely do not have an active infection and no additional follow-up is needed.
  • If you have symptoms and meet other guidelines for testing, you would need another type of test called a nucleic acid test. This test uses respiratory samples, such as a swab from inside your nose, to confirm COVID-19. A serologic test alone cannot tell if you definitely have COVID-19.
  • It’s possible you might test positive for antibodies and you might not have or have ever had symptoms of COVID-19. This is known as having an asymptomatic infection, or an infection without symptoms.
• If you test negative:
  • If you test negative for COVID-19 antibodies, you probably did not have a previous infection that has gotten better. However, you could have a current infection. It’s possible you could still get sick if you have been exposed to the virus recently, since antibodies don’t show up for 1 to 3 weeks after infection.
  • Some people may take even longer to develop antibodies, and some people may not develop antibodies.
  • If you have symptoms and meet other guidelines for testing, you would need another type of test called a nucleic acid test. This test uses respiratory samples, such as a swab from inside your nose, to confirm COVID-19. A serologic test alone cannot tell if you definitely have COVID-19.
• Know How to Protect Yourself and Others

CDC’s Work in Serology Testing

CDC is evaluating commercial tests

CDC is evaluating the performance of commercially manufactured serologic tests in collaboration with other government agencies. FDA has authorized emergency use of several serologic tests.

For more information:

• FDA Emergency Use Authorizations for COVID-19external icon
• FDA: Serological Test Validation and Education Effortsexternal icon

CDC is conducting serologic surveillance

CDC is looking at data from serology tests to estimate the total number of people who have been infected with SARS-CoV-2 in the United States. CDC is also using serologic testing to learn more about how the body’s immune system responds to the virus and to explore how the virus spreads among people exposed to it. The information CDC is looking at comes from many groups, including blood donors and household contacts of people who had symptoms and were diagnosed with COVID-19.

CDC is supporting state, local, tribal and territorial laboratory capacity.