Creatine is a chemical naturally produced by the human body. It is produced in the liver and kidneys from the amino acids L-arginine, L-methionine, and glycine. Nearly 95% of the body’s supply of creatine is contained in the skeletal muscle. Although creatine can be found in fish and meat, it is a popular supplement among athletes because once changed into phosphocreatine, it is stored in the muscles and then used for energy. Bodybuilders especially love it because during short intense bursts of exercise, such as weight lifting, phosphocreatine turns into adenosine triphosphate (ATP), which is what our bodies use for fuel.