Here's how to get your free COVID-19 tests from the government — plus more FDA-authorized options

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At-home COVID-19 tests allow you to know your coronavirus status, whether you've developed symptoms or recently had close contact with someone who is infected. The problem is, these tests can be hard to find.

It's important to note that, starting on Wednesday, the U.S. government will be distributing free COVID-19 tests to households via the website COVIDtests.gov. A sign-up button was added recently, which brings you to a USPS website to enter your name and address. Each residential address will be sent four COVID-19 tests to be used as needed. All you need to do is sign up. The website says that test will ship within seven to 12 days, so it's good to sign up before you actually need tests.

Need a test ASAP, or more than four for your household? At-home COVID-19 tests are now available to the general public at pharmacies, larger retailers and even grocery stores and online — they just often fly off shelves as soon as they're stocked. CVS even has a message on its website, urging people to check back daily if a particular test they're interested in is out of stock, noting that it could be available again the next day.

Still, if you can find one, it's a good idea to grab it. "It makes sense to have a kit on hand, so it’s there if needed," Dr. Amesh A. Adalja, a senior scholar at the Johns Hopkins Center for Health Security, tells Yahoo Life.

Some tests have been granted an emergency use authorization (EUA) by the Food and Drug Administration (FDA), which is a designation used during public health emergencies — like a global pandemic — that says the FDA recognizes that these tests can be used to diagnose COVID-19 and that certain criteria have been met. It's different from full FDA approval, which typically comes only after a longer period of time has passed and more data is collected.

If you've never used an at-home COVID-19 test, you probably have some questions about what, exactly, these are and how they work.

Rapid tests are the most common type. (Some tests will have you collect a specimen and mail it to a lab, where it will be analyzed, but these are less popular, given that they take longer to get results.) Most at-home tests will have you do a nasal swab, per the Centers for the Disease Control and Prevention (CDC), but others will ask you to give a saliva sample. Every test is different, so it's important to read the instructions carefully before you test and while looking at results, the CDC says.

A big question many people have about these tests is how accurate they are. Rapid COVID-19 tests aren't necessarily as accurate as PCR tests, which are considered the gold standard, but they can do a lot. One meta-analysis published in March found that rapid antigen tests picked up about 72 percent of symptomatic cases that were confirmed positive by a PCR test. The rapid tests were less sensitive with asymptomatic infections, though, only confirming 58 percent of those cases.

Each test kit conducts its own research on how effective the company's product is at detecting COVID-19 and, in general, Adalja says they're "adequate" at telling if you're infected or not — especially if you have symptoms.

There are several options out there for at-home COVID tests, but those that are authorized by the FDA have shared their data online. Among some of the more common tests, BinaxNOW says its test detects 84.6 percent of positive COVID-19 cases and 98.5 percent of negative cases, Ellume says its test has 96 percent accuracy in detecting symptomatic cases of COVID-19 and is 91 percent accurate in detecting asymptomatic cases. Fellow EUA test InteliSwab says its test identified 84 percent of positive samples in clinical trials, and 98 percent of negative samples, while QuickVue says its test picks up 83.5 percent of positive cases and 99.2 percent of negative cases. On/Go says its test is 95 percent accurate when used within the first seven days after you developed symptoms, while the iHealth rapid antigen test says it's 94.3 percent accurate at correctly identifying positive cases.

Ultimately, Adalja says, "the best rapid test for COVID is the one you can find."

With that in mind, we tracked down popular at-home COVID-19 tests that are still in stock at press time. Here's where you can find them:

• BinaxNOW: This popular at-home kit involves taking a nasal swab and waiting 15 minutes for your result. You can find it at Walmart for $20 and CVS for $24 (currently sold out, but stock is replenished regularly)

• QuickVue: This test kit has you take a nasal swab, put it in a solution, dip in a test strip and then wait for your results. It's $24 at Walgreens and $24 at CVS (currently sold out, but stock is replenished regularly. You may be able to find it in stores.)

• On/Go: This kit involves taking a nasal swab, putting it in a solution, squeezing a few drops of the solution into a test kit and waiting for your results. There's an app to guide you through the whole process. It's $24 at Amazon and $30 at Walmart for two tests.

• iHealth rapid antigen test: This Amazon bestselling test kit has you take a nasal swab, dip it in a solution, add a few drops of the solution to the test kit and wait for your results. It's $20 at Amazon for two tests.

• FlowFlex: This test was recently authorized by the FDA. It involves swabbing your nose, sticking it in a special solution and analyzing the solution in a test kit. It's $10 at CVS and $8 at Target (currently sold out, but stock is replenished regularly)

Bottom line: If you can find an at-home COVID-19 test right now, it's a good idea to buy one — or a few. You never know when you may need them.

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