The determination of CK-NAC activity in plasma or serum provides a sensitive marker for the detection of skeletal muscle disease; and is also useful to assess the extent of severe muscle trauma, crush injuries, burns or electrocution, and the likelihood of developing rhabdomyolysis.

CPK test. Creatine phosphokinase (CPK) is an enzyme in the body. It is found mainly in the heart, brain, and skeletal muscle. This article discusses the test to measure the amount of CPK in the blood. Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand.

What is normal CK level? In a healthy adult, the serum CK level varies with a number of factors (gender, race and activity), but normal range is 22 to 198 U/L (units per liter). Higher amounts of serum CK can indicate muscle damage due to chronic disease or acute muscle injury.