Creatine Kinase (CK) is the new name of creatine phosphokinase (CPK). CK is an enzyme, a protein necessary for muscle cells of the body to achieve their different chemical reactions. Normally, levels in the blood are low and an increase of its levels indicate a muscular disorder. Indeed, it is increased in cases of destruction of a part of the skeletal muscles (rhabdomyolysis), and in case of failure of the heart muscle in myocardial infarction. There are three main forms of CK. CK-MB (or CPK-MB) characteristic of the cells of the heart, the CK-MM (or CPK-MM) used by those of the muscles and finally CK-BB in the brain.