CK - Creatine Kinase

Also known as: Total CK, Creatine phosphokinase, CPK
Formal name: Creatine Kinase

Why get tested?
To determine if you have had a Heart Attack or if other muscles in your body have been damaged

When to get tested?
If you have signs and symptoms of a heart attack (e.g., Chest pain ); if you have muscle pain or muscular weakness

Sample required?
A blood sample drawn from a vein in the arm

The Test Sample

What is being tested?
Creatine kinase is an enzyme found in the heart, brain, skeletal muscle, and other tissues. Enzymes are proteins that help cells to perform their normal functions. In muscle and heart cells, most of this energy is used when muscles contract.

There are three different forms of CK in your body; they are referred to as isoenzymes:

  • CK-MM (found in your skeletal muscles and heart),  
  • CK-MB (found mostly in your heart),  
  • CK-BB (found mostly in your brain).

The small amount of CK that is normally in the blood comes mainly from your muscles. The CK in your brain almost never gets into the blood.

How is the sample collected for testing?
A blood sample is taken by needle from the arm.

How is it used?
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.

When is it ordered?
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.

What does the test result mean?
NOTE: A standard reference range is not available for this test. Because reference values are dependent on many factors, including patient age, gender, sample population, and test method, numeric test results have different meanings in different labs. Your lab report should include the specific reference range for your test. strongly recommends that you discuss your test results with your doctor.

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.

Is there anything else I should know?
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.

What are the other heart attack tests? 

Doctors often use more than one test to determine if a person who has chest pain is having a heart attack. Troponin is generally considered the most accurate test, and CK-MB (the heart isoenzyme of CK) is also highly accurate in detecting damage to the heart, even when there is no other evidence of a heart attack. Myoglobin and creatine kinase almost always rise in patients with a heart attack, but they are less specific - other conditions can also produce an increase in these two tests.

Provided by ArmMed Media
Revision date: June 18, 2011
Last revised: by David A. Scott, M.D.