Can I use my expired COVID-19 test? Here's how to know

(NEXSTAR) – After stocking up on free COVID-19 tests from the government before the program was suspended in June, some people may be wondering if they can still get accurate results if their swab kits have expired.

If you've recently rummaged for an old test after experiencing a cough or runny nose, you're not alone. U.S. hospitalizations due to COVID-19 have been rising steadily since early July, including a 15% jump over the past week, according to Centers for Disease Control and Prevention data.

But is it safe to use a COVID-19 test that is past the expiration? The answer, it turns out, depends on what brand of test you have.

The FDA has extended that date for a number of different at-home COVID-19 tests. The expiration date for multiple lots of BinaxNow COVID-19 antigen tests that were sold at CVS, for example, is now 10 months later than the printed date.

In January, BinaxNow manufacturer Abbott wrote a letter to consumers to announce testing results showing that the kits had a shelf-life of up to 22 – not 12 – months.

To see if your testing kit is still safe to use, visit the FDA website and check to see if there is an "Extended Expiration Date" link next to your product. By clicking on it, you can find the lot number and new expiration date.

“That’s the first thing I would do before using an expired test or throwing it away,” Andrew Pekosz, a Johns Hopkins Bloomberg School of Public Health professor, told CNBC.

Expired COVID-19 at-home tests shouldn't be used, the FDA warns that the parts they are made of may "degrade, or break down, over time" and give "inaccurate or invalid test results."

"The antibodies used to detect the antigens will degrade over time, so the sensitivity of the tests could be lower if used beyond the expiry date," Dr. Daniel Rhoads, with Cleveland Clinic, told Nexstar in an emailed statement. "The risk in using an outdated test is that it could produce a 'false negative' result more often than expected. That is, the antibodies might not be able to detect the viral antigen as well as when it was first manufactured."

If your test is still good but you get a negative result, the FDA recommends taking a repeat test to help rule out a false negative. If the result is positive, you most likely have COVID-19, the FDA adds.

All at-home COVID tests authorized by the FDA should only be used according to the instructions provided for the most reliable results Rhoads said, adding, "this includes adhering to the recommended expiration dates."