This test measures the amount of creatine kinase (CK) in a sample of your blood. CK is also called creatine phosphokinase (CPK).

CK is an enzyme. An enzyme is a protein that speeds up certain chemical reactions in your body. CK helps make energy. Most of the CK in your body is in your skeletal muscles. These are the muscles you use to move. You also have CK in your heart muscle and small amounts in your brain.

Normally, a small amount of CK gets into your blood from the usual wear and tear on your muscles. But if your muscles, heart, or brain tissues are damaged, larger amounts of CK leak out of your cells into your bloodstream.

A CK test is mainly used to help diagnose and monitor injuries and diseases that damage skeletal muscles and cause high levels of CK in your blood. But it may also be used for conditions that damage the heart muscle and the brain.