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Creatine Kinase (Blood)

Does this test have other names?

Creatine phosphokinase, CK, CPK

What is this test?

This test measures the amount of a protein called creatine kinase (CK) in your blood.

The muscle cells in your body need CK to function. Levels of can rise after a heart attack, skeletal muscle injury, strenuous exercise, or drinking too much alcohol, and from taking certain medications. If this test shows that your CK levels are high, you may have muscle or heart damage.

Why do I need this test?

You may need this test if you have chest pain or weakness and your doctor needs to find out if you've had a heart attack.

Your doctor may also order this test if you have had a stroke or sports injury. But because levels of this protein may not peak for up to two days after certain injuries, you may need this test several times to see if your heart or other muscles have been damaged.

If you are taking statin drugs and experience unusual muscle cramping and pain or muscle weakness, your doctor may also order a CK test. This is because statin drugs sometimes cause serious muscle injury and in very rare cases can even lead to a rapid, life-threatening muscle breakdown.

What other tests might I have along with this test?

Your doctor may order other tests to find out if you have had a heart attack or muscle injury. If you have had a heart attack, your doctor may look for high levels of myoglobins or troponins, other proteins that are also found in your heart, or order tests to see how you are recovering.

These other tests include:

  • Troponin blood test

  • Electrocardiogram, or ECG, to measure the electrical activity of your heart

You may also be tested for an isoenzyme called creatine kinase MB. CK-MB is mainly found in the heart. If you've had a heart attack, your doctor will look at the amount of CK-MB you have in relation to the total CK in your body. Levels of CK-MB that are over 2.5 to 3 percent of your total may mean you have suffered damage to your heart muscle.

Because levels of CK may rise if you have a thyroid problem or kidney failure, your doctor may also order tests to find out how well these organs are working.

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Results are given in units per liter (units/L). The normal range for the general CK measurement depends on your age and gender.  Generally, the normal range is:

  • 55 to 170 units/L for men

  • 30 to 135 units/L for women

  • 68 to 580 units/L for newborns

High CK levels may mask other health problems, such as alcohol abuse or kidney failure.

How is this test done?

The test requires a blood sample, which is drawn through a needle from a vein in your arm.

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

Strenuous exercise, recent surgery, and certain drugs may make your CK levels higher than normal.

African-Americans naturally have higher levels of CK, as do some people with a muscular build.

How do I get ready for this test?

You don't need to prepare for this test. But be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.