If youve been stockpiling COVID-19 test kits in your cabinet, or recently received your free tests from the government , you might want to take note of their use-by dates, as most kits expire within a year.

But even if your kits expiration date is approaching, that doesnt necessarily mean its time to trash it. Most of the expiration dates initially listed on the packaging labels were a prudent estimate based on preliminary stability tests. Over the past couple of years, additional testing has been conducted to determine the true shelf life of the various at-home tests, and, as a result, many test manufacturers have updated their products expiration dates.

That said, youll still want to be mindful of how long your kit is good for. Using a kit thats well past its expiration date could lead to inaccurate results that could give you a false sense of security.

Then you could make decisions based on something thats no good, said Cedric Yansouni , a scientist at the Infectious Diseases and Immunity in Global Health Program at the Research Institute of the McGill University Health Centre.

How quickly the COVID at-home rapid tests expire

The expiration dates vary from brand to brand, but generally range from six months to 15 months from the time theyre manufactured. Abbotts BinaxNOW kits along with Ellumes COVID home tests have a 15-month timeline; the orange iHealth kits are good for nine months .

These expiration dates are based on stability tests the manufacturers conducted during development to estimate the kits shelf lives. But the expiration dates initially listed on the kits packaging labels are most likely conservative.

Typically, when you first market a new product, youre going to be putting out a best-before date or expiry date that you know, for sure, will cover the period during which the product will give you reliable results, Yansouni said.

Eventually, certain rapid test ingredients like the solution in the droppers start to go bad. The whole idea behind the expiration dates is to ensure these components still work well so the tests provide accurate results, which helps people make informed decisions about their health.

The worst thing that can happen is being falsely reassured or falsely alarmed by a test result that was based on a reagent that is no longer valid, Yansouni said.

Expiration dates are changing

Keep in mind that the rapid antigen tests for COVID-19 are relatively new and have only been around for a couple of years. Though the initial stability tests helped manufacturers bring the test to markets quickly, determining the tests true shelf life takes time, as manufacturers must evaluate how the tests hold up over weeks, months, and maybe even years.

Over the past two years, test manufacturers and government agencies have continued to test the kits durability and have updated various test kits expiration dates based on their newer findings.

The BinaxNOW kit, for example, was originally marketed with a 12-month shelf life that has since been extended to 15 months. Similarly, the iHealth kits started with a six-month expiration date that was recently increased to nine months. For both of these kits, you can add three months to the expiration date listed on the box. Ellume currently has a 15-month shelf life, and a 21-month shelf life is currently under review, according to an Ellume spokesperson.

To see if your test kits expiration date has been recently updated, visit the Food and Drug Administrations page on diagnostic tests . Scroll down to the table of tests and enter OTC in the search bar. Then, find the test you are looking for, click on the + symbol to the left of the kit name, and look for a letter granting EUA revisions. You can also call the test kit manufacturer, such as Abbott Diagnostics or Ellume Limited, and ask if theyve updated the expiration date of your specific kit.

Yansouni expects that, eventually, the at-home kits could have a shelf life of up to 24 months, as thats pretty typical of rapid diagnostic antigen tests used for other health conditions.