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If you've been storing your rapid antigen COVID-19 tests, better known as at-home tests, for months and suddenly realized they're expired, you may not need to throw them away. They could still be usable.

The U.S. Food and Drug Administration, which authorizes these tests, has extended the expiration date for about 10 brands of at-home tests. The California Department of Public Health then endorsed the FDA's emergency-use extension earlier this summer.

"In accordance with federal guidance, tests may be used past extended expiration dates if the internal test control continues to function properly," the department told KCRA 3.

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The FDA has a website where it lists all of the authorized at-home test kits. To check if the test you have is still usable, you'll need the lot number on the box.

On July 8, iHealth was given another three-month extension for its tests that were issued on March 29, 2022, according to CDPH. This extended the shelf life from six to 12 months. Click here to look up the new expiration date by lot number.

ACON's FlowFlex tests were given four-month extensions on April 22, 2022. So, that means if the original expiration date says Oct. 2022, it now does not expire until Feb. 2023. Learn more here.

That depends on what brand of at-home COVID-19 test you have.

Some tests like Binax through Abbott Diagnostics have a shelf life of about 15 months. In comparison, iHealth tests have a shelf life of 12 months, which the FDA extended. Then there are some like Lucira Health, which only has a six-month shelf life.

In an interview with CNN, Dr. William Schaffner, professor in the Division of Infectious Diseases at Vanderbilt University Medical Center, said it's based on stability testing.

"Since it takes time for test manufacturers to perform stability testing, the FDA typically authorizes at-home COVID-19 tests with an expiration date of about four to six months from the day the test was manufactured, based on initial study results," he said. "Once the test manufacturer has more stability testing results, such as 12 or 18 months, the test manufacturer can contact the FDA to request that the FDA authorize a longer expiration date. When a longer expiration date is authorized, the test manufacturer may send a notice to customers to provide the new authorized expiration date, so the customers know how long they can use the tests they already have."

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The short answer is yes.

"As long as you haven't abused the test in some way, put it in a deep freeze or left it out in the sun or something like that. Sure. We can rely on the results of the test," Schaffner said.

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