Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.
The White House announced that vaccines will be required for international travelers coming into the United States, with an effective date of November 8, 2021. For purposes of entry into the United States, vaccines accepted will include FDA approved or authorized and WHO Emergency Use Listing vaccines. More information is available here.
Travel requirements to enter the United States are changing, starting November 8, 2021. More information is available here.

COVID-19 Testing: What You Need to Know

COVID-19 Testing: What You Need to Know
Updated Sept. 28, 2022
When you get tested:
  • Make sure to test at the right time
  • Choose the right type of test for your circumstance
  • Follow test directions as recommended by FDA

If you do not, your results may be less likely to correctly indicate whether you have COVID-19 or not.

When to Get Tested for COVID-19

Healthcare worker holding vial and swab

Key times to get tested:

  • If you have symptoms, test immediately.
  • If you were exposed to COVID-19 and do not have symptoms, wait at least 5 full days after your exposure before testing. If you test too early, you may be more likely to get an inaccurate result.
  • If you are in certain high-risk settings, you may need to test as part of a screening testing program.
  • Consider testing before contact with someone at high risk for severe COVID-19, especially if you are in an area with a medium or high COVID-19 Community Level.

For guidance on using tests to determine which mitigations are recommended as you recover from COVID-19, go to Isolation and Precautions for People with COVID-19.

Types of Tests

Viral tests look for a current infection with SARS-CoV-2, the virus that causes COVID-19, by testing specimens from your nose or mouth. There are two main types of viral tests: nucleic acid amplification tests (NAATs) and antigen tests. In certain circumstances, one test type may be recommended over the other. All tests should be performed following FDA’s requirements.

  • NAATs, such as PCR-based tests, are most often performed in a laboratory. They are typically the most reliable tests for people with or without symptoms. These tests detect viral genetic material, which may stay in your body for up to 90 days after you test positive. Therefore, you should not use a NAAT if you have tested positive in the last 90 days.
  • Antigen tests* are rapid tests which produce results in 15-30 minutes. They are less reliable than NAATs, especially for people who do not have symptoms. A single, negative antigen test result does not rule out infection.  To best detect infection, a negative antigen test should be repeated at least 48 hours apart (known as serial testing). Sometimes a follow-up NAAT may be recommended to confirm an antigen test result.

*Self-tests, or at-home tests, are usually antigen tests that can be taken anywhere without having to go to a specific testing site. Follow FDA and manufacturer’s instructions, including for the number of times you may need to test. Multiple negative test results increase the confidence that you are not infected with the virus that causes COVID-19.

  • You can order free self-test kits at or purchase tests online, in pharmacies, and retail stores.
  • You can also visit FDA’s website to see a list of authorized tests.
  • As noted in the labeling for authorized over-the-counter antigen tests: Negative results should be treated as presumptive (meaning that they are preliminary results). Negative results do not rule out SARS-CoV-2 infection and should not be used as the sole basis for treatment or patient management decisions, including infection control decisions. Please see FDA guidance on the use of at-home COVID-19 antigen tests.
About Self-Tests

Choosing a COVID-19 Test

I am in a circumstance where I should get tested and:

I have not had COVID-19 or I have not had a positive test within the past 90 days.

You may choose NAAT or antigen tests.
If you use an antigen test and your result is negative, multiple tests may be necessary.

I tested positive for COVID-19 in the last 90 days.

My first positive test result was within:

30 days or less

I have symptoms
Use antigen tests. If negative, multiple tests may be necessary.

I do not have symptoms
Testing is not recommended to detect a new infection.

My first positive test result was within:

31-90 days

I have symptoms
Use antigen tests. If negative, multiple tests may be necessary.

I do not have symptoms
Use antigen tests. If negative, multiple tests may be necessary

After a positive test result, you may continue to test positive for some time after. You may continue to test positive on antigen tests for a few weeks after your initial positive. You may continue to test positive on NAATs for up to 90 days. Reinfections can occur within 90 days, which can make it hard to know if a positive test indicates a new infection.  Consider consulting a healthcare provider if you have any questions or concerns about your individual circumstances.

Interpreting Your Results

If Your COVID-19 Test is


Any positive COVID-19 test means the virus was detected and you have an infection.

  • Isolate and take precautions including wearing a high-quality mask to protect others from getting infected.
  • Tell people you had recent contact with that they may have been exposed.
  • Monitor your symptoms. If you have any emergency warning signs, seek emergency care immediately.
  • Consider contacting a healthcare provider, community health center, or pharmacy to learn about treatment options that may be available to you. Treatment must be started within several days after you first develop symptoms to be effective.
    • You are more likely to get very sick if you are an older adult or have an underlying medical condition. Possible treatment may be available for you.
If Your COVID-19 Test is


A negative COVID-19 test means the test did not detect the virus, but this doesn’t rule out that you could have an infection. If you used an antigen test, see FDA instructions on repeat testing.

  • If you have symptoms:
    • You may have COVID-19, but tested before the virus was detectable, or you may have another illness.
    • Take general public health precautions to prevent spreading an illness to others.
    • Contact a healthcare provider if you have any questions about your test result or if your symptoms worsen.
  • If you do not have symptoms, but were exposed to the virus that causes COVID-19, you should continue to take recommended steps after exposure.
  • If you do not have symptoms and you have not been exposed to the virus that causes COVID-19, you may return to normal activities.

Need additional help with COVID-19 testing? is an online, mobile-friendly tool that helps you make decisions about COVID-19 testing.

Testing for Antibodies

Antibody or serology tests look for antibodies in your blood that fight the virus that causes COVID-19. Antibodies are proteins created by your immune system after you have been infected or have been vaccinated against an infection. They can help protect you from infection, or severe illness if you do get infected, for a period of time afterward. How long this protection lasts is different for each disease and each person.

Antibody tests should not be used to diagnose a current infection with the virus that causes COVID-19. An antibody test may not show if you have a current infection, because it can take 1 to 3 weeks after the infection for your body to make antibodies.

Science at CDC

Scientific evidence and studies behind specific COVID-19 guidance and recommendations
MMWR: Minimizing the impact of COVID-19 on Individual persons, Communities, and Health Care Systems

Difference Between Flu and COVID-19

Influenza (Flu) and COVID-19 are both contagious respiratory illnesses, but they are caused by different viruses. COVID-19 is caused by infection with a coronavirus named SARS-CoV-2, and flu is caused by infection with influenza viruses. You cannot tell the difference between flu and COVID-19 by symptoms alone because some of the symptoms are the same. Some PCR tests can differentiate between flu and COVID-19 at the same time. If one of these tests is not available, many testing locations provide flu and COVID-19 tests separately. Talk to a healthcare provider about getting tested for both flu and COVID-19 if you have symptoms.

Learn more