Creatine is a natural energy source that is used in muscle and nerve tissue creatine is stored as creatine phosphate phosphocreatine in muscle cells this phosphocreatine is the important factor that forms atp adenosine triphosphate one of the bodys quick energy molecules creatine replaces the atp which has been used up during muscle contraction to allow prolonged intense activity creatine monohydrate supplementation increases phosphocreatine levels in the muscle especially whe