If you are currently being treated with any of the following medications, you should not use creatine without first talking to your health care provider.

Cimetidine, diuretics, NSAIDs, and probenecid -- Creatine may increase the likelihood of damage to the kidneys if taken with cimetidine (Tagamet, a medication used for heartburn and to prevent ulcers), diuretics, probenecid (used for gout), or non-steroidal anti-inflammatory (NSAID) medications (such as ibuprofen or Advil).

Other substances -- The combined use of caffeine, ephedra (a very concerning substance once found in sports or weight loss supplements that was banned in 2004), and creatine has been associated with at least one report of a stroke in a male weight lifter. It is believed that the combination of creatine with herbs and medications that stimulate the central nervous system contributed to the stroke.