Supplement makers in the US aren't held to the same standards of testing by the FDA as prescription drugs are. While supplements are still supposed to be labeled correctly, many aren't.
When you take a prescription drug in the United States, you can be reasonably sure of what's in it. The Food and Drug Administration (FDA) requires that all pharmaceuticals be thoroughly tested in humans, that they contain whatever ingredients are listed on the label, and that they have evidence to back their marketing claims.
When you take a prescription drug in the United States, you can be reasonably sure of what's in it. The Food and Drug Administration (FDA) requires that all pharmaceuticals be thoroughly tested in humans, that they contain whatever ingredients are listed on the label, and that they have evidence to back their marketing claims.