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COVID-19 rapid antigen tests are very popular for detecting COVID-19. Although these at-home tests are less accurate than PCR tests during very early stages of the virus, or when recovering from infection, they are convenient. These rapid tests can be used at home or at school and give results in 15 to 20 minutes.

Below, UC Davis Health experts share what you need to know about COVID-19 rapid antigen tests.

Get at-home COVID test instructions, and information on accuracy and where to find one

Rapid antigen tests search for protein pieces from the coronavirus. For COVID-19 testing, a sterile swab is used to collect samples from both nostrils. The swab is then combined with a liquid (a buffer).

Depending on the test, a swab is placed into a test cartridge, or the liquid is dripped onto the test cartridge itself. If enough protein pieces from the virus are present in the liquid, the test strip will turn positive during the testing time (usually 15 to 20 minutes). Because low levels of a virus may not be detected, it's recommended people test at least twice over a 36- to 48-hour period to increase the odds of detecting an infection.

Learn more about COVID-19 testing

See which COVID-19 symptoms you should watch for

Read the manufacturer's instructions on the at-home COVID-19 test before using it. For an at-home test, you will likely insert a swab device into your nose and then test the specimen. Be sure to follow the maker's instructions or your test results may be inaccurate. Wash your hands before and after you collect a nasal specimen.

Watch this CDC video on how to use an at-home test

Learn more about at-home COVID-19 tests from the CDC

Antigen tests are known to be less sensitive than PCR tests. These COVID rapid tests perform best when people with high viral loads test within a few days after COVID-19 symptoms appear. In people who have no symptoms, the sensitivity is improved by repeat testing over 36 to 48 hours.

It is important to follow the testing instructions that come with the test to ensure the quality of the results. For example, if a collection swab isn’t inserted deep enough into the nose or not swabbed the recommended number of times, it may not collect a good sample for testing. Then the test may give a false negative.

No test is completely accurate. This means that some cases will be missed (false negatives), and some people will be told they have COVID-19 when they don’t (false positives). Positive tests tend to be accurate. Negative tests need to be interpreted with caution. This is especially true in high-risk settings where there are people vulnerable to severe disease from COVID-19 (due to age or chronic medical conditions, etc.) or when the test is used on asymptomatic people. However, some experts argue that widespread testing, even when it's less accurate, can help contain COVID-19, especially if the test is regularly repeated.

You can buy an over-the-counter rapid antigen self-test kit for $20 to $30 online or at drugstores (although they sometimes sell out quickly). These at-home kits usually come with two tests, and you can use an app to track your results.

The Center for Medicare and Medicaid Services has set up a new program where people can get reimbursed for tests through their insurance company. Get more information on how to get your rapid antigen test

The U.S. government is also providing free at-home COVID-19 rapid tests. The tests are delivered by USPS. Each order contains four individual tests. There is a limit of 1 order per household.Order your rapid antigen test kit from the federal government

COVID-19 testing locations, which you can find through California’s COVID-19 website, offer different types of COVID-19 tests, including antigen and PCR tests. You can also find testing locations through county websites:

UC Davis Health patients and non-patients with COVID-19 symptoms can contact a doctor through UC Davis Express Care or by contacting their primary care provider through MyUCDavisHealth.

Learn more about COVID-19 testing

If you were exposed to someone with COVID-19 and have symptoms but test negative on an at-home test, you should take a PCR test. These tests are more sensitive than the rapid at-home tests.

At this time, there is no indication that rapid antigen tests perform any differently with the omicron variant compared to previous COVID-19 variants. This is due to antigen tests targeting proteins that are not likely to change with the different mutations. Manufacturers routinely monitor and test for new variants and have reminded customers that testing performance remains acceptable.

Get the latest on the COVID-19 omicron variant

Early in the omicron surge, some concerns were raised that throat swabs may be better for detecting omicron compared to nasal swabs. UC Davis Health has not seen this difference. Both manufacturers and the FDA have discouraged patients from attempting to obtain a throat swab. Not all supplied swabs are suitable for this use. Collection by untrained person could be dangerous. Patients should follow manufacturer instructions when testing for COVID-19.

Yes, the U.S. Food and Drug Administration (FDA) has given emergency use authorization for hundreds of tests, including over-the-counter rapid tests that can be used at home without a prescription. Tests include BinaxNOW COVID-19 Ag Card, Ellume Lab COVID Antigen Test, Sofia SARS Antigen FIA, InteliSwab COVID-19 Rapid Test Rx and many others.

View the FDA's list of approved at-home antigen tests

If you have serious symptoms of illness, contact your primary care provider. UC Davis Health patients can use the MyUCDavisHealth symptom tracker to evaluate whether to seek help. Telehealth video visits and Express Care are also available.

If you think you've been exposed to COVID-19, please see current testing information.

If you have a medical emergency, call 911 and notify them of your COVID-19 symptoms.

To help limit spread of COVID-19, we have policies for visits to our hospital and outpatient clinics.

UC Davis Medical Center visitor policy

Outpatient clinic policy for caregivers

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