After a brief break, the U.S. government restarted its free at-home Covid test program (order here). Washington's Say Yes! Covid Test is still chugging along—eligible households can order up to 10 free tests each month.

Whether you've already stockpiled a bunch of tests or these are the first at-home kits to grace your mailbox, something might give you pause as you rip open the package: the expiration dates.

Many perturbed Washingtonians have noticed their test kits appear to be expired, often back in June or July. Turns out, the Food and Drug Administration extended the approved shelf life of various at-home tests: iHealth (the one generally sent in the Say Yes! program), Flowflex, and BinaxNow all have updated shelf lives of between 12 to 21 months. Most tests were originally authorized with shelf lives of around four to six months. You can review the list of Covid tests granted extensions on the FDA's website or by lot number on the iHealth website.

The whole situation may feel shady, but the new expiration dates are backed up. The original process to determine expiration dates is stability testing, but the hurried mass rollout of at-home Covid tests didn’t allow for enough time to undergo real-time testing and gauge the length of effectiveness. Manufacturers used a form of accelerated testing, where they stored the tests at higher temperatures for shorter periods, which yielded the shorter shelf lives.

As time passed and real-time stability testing could be performed, further data proved that the tests last way longer than initially thought, which is great news for everyone groaning at the supposedly expired test in their hands.

The extensions are pretty significant, but don’t assume this means they’re effective forever. You won’t get accurate test results if you use tests past the new expiration dates. But, hey, there's always a PCR test.