Creatine is a naturally occurring substance in the human body that does not stunt growth, states Muscle & Strength LLC. Creatine provides energy to muscles, promotes protein synthesis, increases cell volume and acts as a lactic acid buffer.
Most people can take creatine with no negative effects, according to WebMD; however, side effects may occur on rare occasions, especially with excessive use. Possible side effects include weight gain, fatigue, nausea or kidney problems. People with diabetes, liver problems or kidney disease should not take creatine. In addition, minors and pregnant or nursing women should not take creatine supplements. Researchers have yet to determine the long-term side effects of creatine.