At a glance

Also known as

CK

Why get tested?

To determine if muscles in your body have been damaged. Previously used to determine if you are having a heart attack.

When to get tested?

If you have chest pain or muscle pain and weakness

Sample required?

A blood sample drawn from a vein in the arm

What is being tested?

Creatine kinase is an enzyme found in the heart, brain and skeletal muscle. Enzymes are proteins that help cells to perform their normal functions. CK occurs in three major forms, called isoenzymes:

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

CK 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.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

Blood levels of CK rise when your muscle or heart cells are injured. Your doctor requests measurement of CK (along with tests for other substances, particularly the CK-MB form) if you have chest pain to see if you may have had a heart attack. In the first 4 to 6 hours after a heart attack, CK in blood begins to rise. It reaches its highest level after about 18 to 24 hours, and returns to normal in about 2 to 3 days. The test for CK can also indicate if your other muscles are damaged.

When is it requested?

It can be requested if your doctor suspects a heart attack. However, currently the use of CK as a marker of heart attack has been superseded by more specific tests such as cardiac troponin I or T.

If you have muscle pain or weakness, your doctor may order CK to see if skeletal muscles have been damaged.

What does the test result mean?

Looking for reference ranges?

A high CK, or one that increases usually indicates that there has been some damage to the heart or other muscle. It can also indicate that your muscles have experienced heavy use, for example if you have exercised excessively. If your doctor suspects a heart attack and your CK is high, they will usually also request 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 (for example a young fit male will have more muscle mass and hence a higher CK level than an elderly female), and Afro-Caribbeans may have higher CK levels than other ethnic groups. Raised CK levels can also be seen in those with hypothyroidism. 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 after an injection, can also increase CK. 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.

Common Questions

What does heart attack mean?

Heart attack means that some of the muscle in your heart has died. A medical term for this is myocardial infarction (MI). Most commonly, a heart attack starts with a kind of heavy pressure or pain in the chest, often extending into the neck or left arm. You may have trouble catching your breath, or you may feel weak and break into a cold sweat.

A heart attack usually occurs because one of the blood vessels (called coronary arteries) that bring blood to your heart muscle is blocked. This happens when a blood clot forms in a blood vessel that is already partially blocked. The partial blockage, which happens gradually over many years, is usually caused by too much fat layered in the wall of the blood vessel (this is often called hardening of the arteries — the medical term for this is atherosclerosis).

If I have chest pain, does that mean I am having a heart attack? 

Many other problems can cause chest pain, and it is not always possible to tell just from the type of chest pain whether or not you are having a heart attack. Many people have chest pain from straining the muscles in their chest, and chest pain can occur with some lung problems. Chest pain can be a warning sign of hardening of the arteries of the heart called coronary artery disease (CAD). Chest pain that occurs during exercise, hard work or at times of stress, lasts for a few minutes and goes away with rest is called angina. If the pain lasts longer than just a few minutes, especially if it occurs when you are resting, seek immediate medical attention.

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 as the most accurate test. Myoglobin and creatine kinase rise in patients with a heart attack, but they are less specific. CK-MB may also be used.

What if I am not sure I am having a heart attack? 

If you have prolonged chest pain, especially if it does not go away with rest — or if you have been told you have angina, and the drugs you were prescribed do not ease the pain — seek immediate medical attention.