Creatine is a nitrogenous organic acid that occurs naturally in vertebrates. It is synthesized in the liver and kidneys from the amino acids arginine, glycine, and methionine. In the body, creatine is primarily stored in skeletal muscle as phosphocreatine, where it serves as a rapid source of energy during high-intensity, short-duration activities by donating a phosphate group to ADP to regenerate ATP. It is widely used as a dietary supplement to enhance athletic performance, increase muscle mass, and support recovery. Chemically, it exists in equilibrium with its cyclic form, creatinine. The compound is stable under normal conditions but decomposes at high temperatures. Research from peer-reviewed studies supports its efficacy and safety for healthy adults when used at recommended doses of 3-5 g per day.