Creatine Kinase MB (Blood)

Does this test have other names?

CK-MB

What is this test?

This test measures the amount of an isoenzyme of creatine kinase (CK) in your blood. It is called CK-MB.

Your body makes 3 forms of CK, including CK-MB. CK is found in the heart, muscles, and other organs. These include the small intestine, brain, and uterus.

If you have a heart attack, injured heart muscle cells release CK-MB into your blood.

Because many tissues contain CK, high levels of CK can be a sign of a variety of problems. Higher CK-MB may point more directly to heart damage.

Each year millions of Americans go to the emergency room with chest pain, but only a small amount of those people are having a heart attack or other serious, sudden heart problem. This test helps your doctor figure out if you're having a heart attack.

Measuring CK-MB used to be a common tool for diagnosing heart attacks, but doctors use it less often today. Cardiac troponin is now the blood test of choice for finding a heart attack. This is because cardiac troponin is more specific and more sensitive than CK-MB. 

Why do I need this test?

You may need this test if your doctor thinks you are having a heart attack. Symptoms of a heart attack often include:

• Pain or discomfort in the chest, such as a squeezing sensation or feeling of fullness.

• Pain in the neck, back, left arm, or jaw.

• Shortness of breath.

• Feeling lightheaded or dizzy.

• Nausea or vomiting.

• Sudden sweating.

• Tiredness.

What other tests might I have along with this test?

Your doctor may also order a test to measure cardiac troponin. This test is more often used than CK-MB because it more specifically shows heart damage.

Your doctor may also order an electrocardiogram (ECG). This is done to measure electrical activity in your heart and help diagnose a heart attack.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your doctor what your test results mean for you.

Levels of CK-MB do not rise in your blood within the first 4 to 6 hours after a heart attack. You may need to have repeated tests to see if you've had a heart attack.

Higher levels of CK-MB may mean that you have had a heart attack or have other heart problems. These include:

• Myocarditis. This is an infection and inflammation of the heart muscle.

• Pericarditis. This an infection and inflammation of the thin sac that surrounds the heart.

Higher levels of CK-MB may also mean more of the heart was damaged in the attack.

Higher levels may also be caused by muscle damage elsewhere in your body, by diseases that affect your muscles, and by trauma to your chest.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle has some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect my test results?

Timing is important. If you have the test too soon after a heart attack, you may have a false-negative result.

Strenuous exercise and cocaine use can also affect your results.

How do I get ready for this test?

You don't need to prepare for this test.

Tell your doctor about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.