For the use of creatine to increase athletic performance, see Creatine supplements. Not to be confused with creatinine. Creatine (/ˈkriːətiːn/ or /ˈkriːətɪn/) is a nitrogenous organic acid that occurs naturally in vertebrates and helps to supply energy to all cells in the body, primarily muscle.This is achieved by increasing the formation of adenosine triphosphate (ATP).reatine (/ˈkriːətiːn/ or /ˈkriːətɪn/) is a nitrogenous organic acid that occurs naturally in vertebrates and helps to supply energy to all cells in the body, primarily muscle.