By now, there's a good chance that you've stockpiled some at-home COVID-19 tests.

While it may be tough for the average person to really know which brands are best, you will definitely want to stay away from three brands -- Celltrion, ACON Laboratories, and SD Biosensor.

The Food and Drug Administration (FDA) is warning the public about these manufacturers in particular.

The agency is "concerned about the risk of false results when using" certain COVID-19 antigen tests by the aforementioned companies.

Each company has actually issued its own recalls for its particular kits.

In particular, you should avoid the following:

Celltrion DiaTrust COVID-19 Ag Rapid Test found in bright green and white packaging.

Food and Drug Administration
Food and Drug Administration
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ACON Laboratories Flowflex SARS-CoV-2 Antigen Rapid Test (Self-Testing) found in a dark blue box.

Food and Drug Administration
Food and Drug Administration
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SD Biosensor's Standard Q COVID-19 Ag Home Test found in a white and magenta box.

Food and Drug Administration
Food and Drug Administration
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If you tested recently with one of these at-home kits and have concerns about your test results, the FDA urges you to talk to your health care provider.

Also, if you think you had a problem with one of these three tests, the FDA encourages you to report the problem through the MedWatch Voluntary Reporting Form.

Answers to 25 common COVID-19 vaccine questions

Vaccinations for COVID-19 began being administered in the U.S. on Dec. 14, 2020. The quick rollout came a little more than a year after the virus was first identified in November 2019. The impressive speed with which vaccines were developed has also left a lot of people with a lot of questions. The questions range from the practical—how will I get vaccinated?—to the scientific—how do these vaccines even work?

Keep reading to discover answers to 25 common COVID-19 vaccine questions.