While powdered creatine is stable and has a long shelf life if kept in a sealed container, experts suggest that it should be thrown away after two years. Liquid creatine begins to go bad as soon as it is opened, however, and unused portions should not be saved after opening.
While the human body is capable of producing creatine in limited quantities, the supplement is often used by weight lifters and bodybuilders. As it is a natural amino acid, it is safe to consume provided that an ample amount of water is also ingested. Too much creatine, however, can cause serious side effects.