Supplement brands like to present themselves as spotless. A clean website, a confident label, a wall of five-star reviews. None of that tells you whether a regulator has ever written to the company and told it to stop. That information is public, and checking it takes about ten minutes.

In the United States, the Food and Drug Administration publishes warning letters on its website. These are formal letters sent to companies that have broken the rules — making disease claims a supplement cannot legally make, selling a product that contains an undeclared ingredient, or operating a facility that failed inspection. The letters are searchable by company name. A brand that has received one will usually have cleaned up its act afterwards, but the letter itself remains on the record, and the history is worth knowing.

The search itself is straightforward. Find the FDA warning-letters database, enter the brand name exactly as it appears on the label, and read what comes back.…