The creatine phosphokinase test is used to measure the amount of CPK enzyme in the blood, explains MedlinePlus. Creatine phosphokinase is an enzyme found in the skeletal muscles, brain and heart.
The CPK test is used to diagnose heart attack and muscle diseases, evaluate the underlying cause of chest pain, determine if a muscle has sustained damage and differentiate between postoperative infection and malignant hyperthermia, notes MedlinePlus. A normal CPK level ranges from 10 to 120 micrograms per milliliter. Heart attack, brain injuries, muscular dystrophy, electric shock and inflammation of the heart muscle are potential causes of an elevated CPK level. A lower-than-normal CPK level is sometimes seen in cases of hypothyroidism and hyperthyroidism.