Possible harmful side effects of taking creatine include muscle cramps, diarrhea, upset stomach, high blood pressure, liver dysfunction and kidney damage, as reported by the University of Maryland Medical Center. People with kidney disease, high blood pressure or liver disease should not take this supplement.
Creatine is a chemical normally found in the muscles of the body. It's responsible or making the energy muscles need for body movement, according to WebMD. Athletes commonly use creatine supplements to improve strength, and doctors sometimes recommend creatine supplementation for patients suffering from conditions such as congestive heart failure, depression, bipolar disorder and Parkinson’s disease.