 Health experts recommend looking for one of three quality assurance seals, Consumer Lab, USP, or NSF. You can trust these seals because the testing is done by independent organizations. The USP, NSF, and Consumer Lab seals mean a product contains what's on the label, is free of tested contaminants, and disintegrates fast enough to enter the bloodstream. However, they do not mean the product delivers the promised health benefits. Finally, your doctor needs to know if you take supplements because they can interfere with the other drugs you're taking.