Does the fda regulate supplements as well as medication?

No: However, in Europe the equivalent of FDA does regulate herbal medications.

They tried--failed.: Lobbyists of the makers of OTC medications call up massive protest letters and phone calls to congress whenever the FDA has tried to regulate OTC medications. The label may claim anything, A recent study of OTC products by independent certified testing labs like the U.S. Phamacopeia found that about half did not contain the dose claimed, or contained others.