Creatine is an amino acid derivative formed in the liver
, kidneys, and pancreas from the amino acids arginine, glycine, and methionine. It is found in red meat and fish.
Creatine is not a muscle builder. It aids in the body production of ATP, a fuel, for short, intense bursts of energy. In humans, it builds lean body mass by helping the muscle work longer, allowing one to train harder, lift more weight, and have more repetitions. It is the increase in exercise which results in building muscle, not creatine alone.
No long-term studies have been performed to determine long-term effects of creatine use. Short-term use of low doses in humans appears to be safe. Side effects seen in humans include muscle cramping, muscle strains/pulls, upset stomach, dehydration, weight gain due to water retention, and diarrhea.