You wake up one morning feeling off—your throat feels scratchy, your face is a little hot, and you could spend at least eight more hours in bed. Nearly three years into the COVID pandemic, you know what to do: take an at-home test.
You’ve had rapid tests stored in your closet for months, but now they’re all past their expiration dates. But is it OK to use an expired COVID test—even one just slightly past its use-by date—in a pinch?
“The short answer is no,” Ryan Relich, PhD, medical director of the division of clinical microbiology at Indiana University Health, told Health. But that answer depends on the true expiration date on the rapid test—and it may not be the one printed on the side of the box.
Here's what to know about expiration dates on COVID rapid tests, and when you may be able to still use one that appears expired on the box.
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Determining the True Expiration Date of COVID Rapid Tests
When COVID-specific rapid antigen tests were first approved, they hadn’t been around long enough for manufacturers to study their long-term shelf life, according to Sanjat Kanjilal, MD, MPH, associate medical director of clinical microbiology at the Brigham & Women’s Hospital in Boston and instructor at Harvard University.
Because of that, test manufacturers and the Food and Drug Administration (FDA)—the agency in charge of approving and monitoring such health devices—erred on the safe side. Those initial expiration dates are printed on the tests’ packaging.
But now, the tests have been around long enough to measure their accuracy in the long term, and the FDA has continued to collect data about the tests' true shelf lives. In some cases, it has approved extensions on the expiration date for a number of brands.
That's when you can use what appears to be an expired rapid test—if the FDA has extended its expiration date, according to Relich.
Before you use a COVID rapid test, it's wise to first check the expiration date, and if it's past its shelf life, check the FDA website to determine if your particular rapid test's shelf life has been extended.
The FDA has compiled a list of 23 different at-home COVID tests along with their most accurate and up-to-date expiration dates. The iHealth COVID-19 Antigen Rapid Test, for example—the one sent via mail by the government—has an extended shelf life of 12 months. The FDA now says that if the box of that specific test has an expiration date of August 2022, you may now safely use it until February 2023.
But the FDA is the final word on whether a rapid test is still OK to use.
“If the test is older than the expiration date on the FDA website, I would not use it,” said Dr. Kanjilal.
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Expired Tests Lead to Unreliable Results
COVID rapid tests typically contain two components that are subject to expiration: vials of liquid and testing strips.
The vial liquid is a solution that, when it comes into contact with SARS-CoV-2, prompts the virus to release its antigen proteins. The test strip contains SARS-CoV-2-antigen-specific antibodies, which have been conjugated with luminescent indicators. When the antigen proteins come into contact with the antigen-specific antibodies, an additional colored line appears on the test, indicating a positive result.
Over time, those components of the rapid tests can break down, making the test less sensitive and less reliable.
“If the antibodies or antigens printed on the rapid test have degraded, it could lead to a higher likelihood that the proteins in the patient sample fail to bind and that leads to false negatives,” said Dr. Kanjilal.
The degradation of these tests is why results from expired antigen tests shouldn't be wholly trusted.
“If a person chooses to use an expired at-home test device, the results should be confirmed with a test that is not expired,” said Relich.
According to Dr. Kanjilal, this goes for both positive and negative test results. “We feel less confident in both directions, it’s just hard to say,” he said.
The most important factor is the probability a person was infected with COVID before taking the test, he added: “If they have symptoms or had a known close contact, then a positive test is more believable than if it appeared in someone with no known exposures.”
That doesn’t mean that you’re in the clear if you don’t have any known exposure. Center for Disease Control (CDC) COVID tracking data shows cases have been rising in the US since mid-October.
According to Dr. Kanjilal, if you have a positive at-home test but no symptoms and no known COVID exposure, you should definitely follow up with a PCR. If you have symptoms but have a negative at-home test, you should confirm the result with a PRC, which is more accurate, but can take a few days to produce results.
If you can avoid it, don’t use an expired test at all, Dr. Kanjilal advised. Instead, go right for a fresh rapid test or PCR.
There are already a lot of variables that contribute to when and if a person tests positive for COVID. “When you add the extra variable of an expired test, the pathways become even more uncertain and complex,” said Dr. Kanjilal.
If you have expired tests at home that have not had their expiration date extended, you can dispose of them in your normal trash and replace them with new ones.