Illustration of coronavirus

Although the COVID vaccine and booster shots can reduce our chances of getting a serious case of COVID-19, testing for COVID is still an important part of keeping the virus in check, whether you are vaccinated or not. 

Types of COVID Tests

An important distinction between COVID tests is whether they are diagnostic (sometimes called viral) tests or antibody tests (also called serological tests).

Diagnostic COVID Test

Diagnostic COVID tests look for the presence of an active COVID infection. Typically they are performed by swabbing the inside of the nose. Commonly used diagnostic tests include:

  • PCR tests look for genetic material from the virus and can detect even very small amounts of SARS-CoV-2 (the virus that causes COVID-19) in the earliest stages of infection. These tests may remain positive, however, even after someone has recovered from infection and is no longer contagious. These are typically performed in a medical setting, and the results are usually available in 1-2 days.
  • Antigen tests, which are typically rapid tests, look for the presence of the protein markers associated with SARS-CoV-2. They are best used to detect when a person is carrying a large amount of virus in their body and are most contagious, typically in the first week of infection. They may not detect a very early infection or one that is at its tail end. Their results are typically available within 15-30 minutes. The over-the-counter, in-home tests are antigen tests.

Antibody COVID Test

These blood tests, often done with a finger stick, detect antibodies that your immune system makes to fight COVID-19. But they can only indicate if you have had a past infection, not if you are currently infected. These tests remain positive for months in most people.

Where to Get Tested

Emergency rooms are not an appropriate place to seek COVID testing. Learn more about When to Go to the Hospital.

Urgent care centers, health departments and testing clinics offer testing by appointment and sometimes on a walk-in basis. Be sure to call or check the testing locations website to confirm whether it takes walk-ins.

The Maryland Department of Health COVID Test Finder allows you to screen for tests by:

  • Location
  • Rapid screening
  • Costs
  • Appointment not required
  • Pediatric testing
  • Online scheduling

At-Home Testing

Self-tests, also called at-home or over-the-counter tests, are available to anyone. You do not need to have COVID symptoms or be vaccinated to take a self-test. Self-tests can be bought online, in pharmacies and retail stores or may be available from local community and government organizations.

You may also order free home test kits from Each home in the United States is eligible to receive 4 tests kits through the mail.

The Centers for Disease Control (CDC) says that self-testing can help reduce the spread of COVID-19, but it should be combined with getting vaccinated, wearing a mask and social distancing.

When using an at-home test, follow the manufacturer's directions carefully.

  • If your test is positive it is likely that you have a COVID-19 infection. Stay home, then tell anyone you have been in close contact with that you have tested positive.
  • If your test is negative, it does not mean that you do not have COVID but means that you are not shedding a large amount of virus at that time and are less likely to be contagious. A second at-home test done at least 24 hours after the first test makes it more likely that you are not infected. If you are experiencing COVID-19 symptoms but have negative at-home tests, you should still get a diagnostic test from a healthcare provider as soon as possible as you may still have COVID-19. 

Reasons to Get a COVID Test

If You Have Symptoms

  • Whether you are fully vaccinated or not, if you have symptoms of the coronavirus, you should get a test and stay home and away from others.
  • Call ahead to the testing location if possible to let them know you are symptomatic because many test providers may have different procedures for people with symptoms.

If You Were Exposed to COVID-19

  • You should wear a well-fitting mask around others for at least 10 days if you were exposed to the virus, regardless of your vaccination status or whether you have symptoms.
  • Currently, the CDC says, if you do not have symptoms, test after 5 days. If you are not fully vaccinated and boosted, the CDC has additional recommendations for quarantining, including staying home for 5 days.
  • As we better understand how the COVID-19 vaccines protect us from infection, CDC continues to adapt its guidance for quarantine after exposure. Check the CDC's website for the latest guidance.

If You Need Routine Testing

  • Taking a routine COVID test before attending an indoor, in-person event or visiting vulnerable or unvaccinated individuals can help reduce the spread of the virus.
  • In addition, some workplaces and other organizations routinely test people who don't have symptoms for COVID, including those who are vaccinated.
  • If you are fully vaccinated, your workplace may still require testing. In October 2021, the CDC provided updated guidance on workplace testing. So it will likely depend on your employer and your working conditions if you will be tested at work.

If Your Healthcare Provider Requests It

  • Often patients who are scheduled for surgery or a procedure will need to get a COVID test, typically a PCR test, prior to the procedure. Check with your healthcare provider for details about the timing and type of test.
  • At University of Maryland Medical System (UMMS), for example, we require a PCR test within 96 hours of surgery, and we test all patients upon hospital admission regardless of symptoms.

If You Are Traveling

Whether you are traveling domestically or internationally, please check the latest updates on travel at the CDC website.

Updated 2/28/23

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