What is Creatinine Kinase/Creatinine Phosphokinase (CK/CPK)?

Also Known As: CK Total CK Creatine Phosphokinase CPK

Creatine kinase (CK) is an enzyme found in the heart, brain, skeletal muscle, and other tissues. Increased amounts of CK are released into the blood when there is muscle damage. This test measures the amount of creatine kinase in the blood.

The small amount of CK that is normally in the blood comes primarily from skeletal muscles. Any condition that causes muscle damage and/or interferes with muscle energy production or use can cause an increase in CK. For example, strenuous exercise and inflammation of muscles, called myositis, can increase CK as can muscle diseases (myopathies) such as muscular dystrophy. Rhabdomyolysis, an extreme breakdown of skeletal muscle tissue, is associated with significantly elevated levels of CK.

How is it used?

A creatine kinase (CK) test may be used to detect inflammation of muscles (myositis) or muscle damage due to muscle disorders (myopathies) such as muscular dystrophy or to help diagnose rhabdomyolysis if a person has signs and symptoms. CK may be ordered along with other blood chemistry tests such as electrolytes, BUN, or creatinine (to evaluate kidney function). Urine myoglobin may also be ordered.

A person may have muscle injury with few or nonspecific symptoms, such as weakness, fever, and nausea, that may also be seen with a variety of other conditions. A healthcare practitioner may use a CK test to help detect muscle damage in these cases, especially if someone is taking a drug such as a statin, using ethanol or cocaine, or has been exposed to a known toxin that has been linked with potential muscle damage. In those who have experienced physical trauma, a CK test may sometimes be used to evaluate and monitor muscle damage.

A series of CK tests may be used to monitor muscle damage to see if it resolves or continues. If a CK is elevated and the location of the muscle damage is unclear, then a healthcare practitioner may order CK isoenzymes or a CK-MB as follow-up tests, to distinguish between the three types (isoenzymes) of CK: CK-MB (found primarily in the heart muscle), CK-MM (found primarily in skeletal muscle), and CK-BB (found primarily in the brain; when present in the blood, it is primarily from smooth muscles, including those in intestines, uterus or placenta).

The CK test was once one of the primary tests ordered to help diagnose a heart attack, but in the U.S., this use of CK has been largely replaced by the troponin test. However, the CK test may sometimes be used to help detect a second heart attack that occurs shortly after the first. (For more, see Common Questions.)