Creatine monohydrate

Creatine monohydrate is the most widely used and most thoroughly researched form of creatine — a nitrogen-containing organic acid that your body already makes on its own. Chemically, it is a creatine molecule crystallized with one molecule of water (hence "monohydrate"), which makes it a stable, shelf-stable powder.

Your body synthesizes roughly 1 g/day in the liver and kidneys, and you get another 1–2 g/day from red meat and fish. About 95% of it is stored in skeletal muscle, with the rest in the brain, heart, and testes. Vegetarians typically have lower muscle creatine stores, which is one reason they often respond more noticeably to supplementation.