Blood levels of CK rise when muscle or heart cells are injured. Your doctor may test for CK if you have chest pain or other signs and symptoms of a heart attack. In the first 4 to 6 hours after a heart attack, the concentration of CK in blood begins to rise. It reaches its highest level in 18 to 24 hours and returns to normal within 2 to 3 days. The amount of CK in blood also rises when skeletal muscles are damaged.

CK is ordered in patients who may have had a heart attack. The test will usually be ordered when a patient arrives at the emergency room and again at intervals of 4-6 hours for a total of three tests. If you have muscle pain or weakness, your doctor may also order CK to see if other muscles have been damaged.

A high CK, or one that goes up from the first to the second or later samples, generally indicates that there has been some damage to the heart or other muscles. It can also indicate that your muscles have experienced heavy use. If your doctor suspects a heart attack and your CK is high, she will usually order a more specific test (troponin or CK-MB) to see if your heart is damaged.

People who have greater muscle mass have higher CK levels than those who don’t, and African-Americans may have higher CK levels than other ethnic groups. Very heavy exercise (such as in weight lifting, contact sports, or long exercise sessions) can also increase CK.

Other forms of muscle damage, such as from a fall, a car accident, surgery, or a shot, can also increase CK. Several drugs can increase CK levels. Drinking too much alcohol slightly increases CK. Rarely, some drugs, particularly cholesterol-lowering drugs (statins), can damage muscle and increase CK. If you are taking one of these drugs, let your doctor know if you experience any muscle pain or weakness. Early pregnancy can decrease CK levels.