Creatine is a naturally occurring compound made from three amino acids — glycine, arginine, and methionine. Your body produces about half of what it needs in the liver, kidneys, and pancreas. The rest comes from dietary sources, primarily meat and fish. About 95% of the body's creatine is stored in skeletal muscle, with the remainder distributed in the brain, heart, and other tissues.

Creatine's primary role is straightforward: it helps your cells recycle ATP, the molecule every cell in your body uses for energy. When ATP releases energy, it loses a phosphate group and becomes ADP. Creatine, stored as phosphocreatine, rapidly donates its phosphate group back to ADP, regenerating ATP. This process is especially important in tissues with high or fluctuating energy demands — like muscles during exercise and the brain during demanding cognitive tasks.