Also Known As
CK
Total CK
Creatine Phosphokinase
CPK
Formal Name
Creatine Kinase
This article was last reviewed on
This article waslast modified on August 2, 2018.
At a Glance
Why Get Tested?

To detect and monitor muscle damage; to help diagnose conditions associated with muscle damage; for heart attack detection, this test has been largely replaced by troponin T and I – markers more specific to cardiac tissue; however, it may sometimes be used to help detect a second or subsequent heart attack (see Common Questions #4).

When To Get Tested?

When you have muscle weakness, muscle aches, and/or dark urine and your healthcare practitioner suspects muscle damage; sometimes to monitor for muscle injury resolution or persistence

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Creatine kinase (CK) is an enzyme found in the heart, brain, skeletal muscle, and other tissues. Increased amounts of CK are released into the blood when there is muscle damage. This test measures the amount of creatine kinase in the blood.

The small amount of CK that is normally in the blood comes primarily from skeletal muscles. Any condition that causes muscle damage and/or interferes with muscle energy production or use can cause an increase in CK. For example, strenuous exercise and inflammation of muscles, called myositis, can increase CK as can muscle diseases (myopathies) such as muscular dystrophy. Rhabdomyolysis, an extreme breakdown of skeletal muscle tissue, is associated with significantly elevated levels of CK.

How is the sample collected for testing?

A blood sample is taken by needle from a vein in the arm.

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

No test preparation is needed.

Accordion Title
Common Questions
  • How is it used?

    A creatine kinase (CK) test may be used to detect inflammation of muscles (myositis) or muscle damage due to muscle disorders (myopathies) such as muscular dystrophy or to help diagnose rhabdomyolysis if a person has signs and symptoms. CK may be ordered along with other blood chemistry tests such as electrolytes, BUN or creatinine (to evaluate kidney function). A urine myoglobin may also be ordered.

    A person may have muscle injury with few or nonspecific symptoms, such as weakness, fever, and nausea, that may also be seen with a variety of other conditions. A healthcare practitioner may use a CK test to help detect muscle damage in these cases, especially if someone is taking a drug such as a statin, using ethanol or cocaine, or has been exposed to a known toxin that has been linked with potential muscle damage. In those who have experienced physical trauma, a CK test may sometimes be used to evaluate and monitor muscle damage.

    A series of CK tests may be used to monitor muscle damage to see if it resolves or continues. If a CK is elevated and the location of the muscle damage is unclear, then a healthcare practitioner may order CK isoenzymes or a CK-MB as follow-up tests, to distinguish between the three types (isoenzymes) of CK: CK-MB (found primarily in heart muscle), CK-MM (found primarily in skeletal muscle), and CK-BB (found primarily in the brain; when present in the blood, it is primarily from smooth muscles, including those in intestines, uterus or placenta).

    The CK test was once one of the primary tests ordered to help diagnose a heart attack, but in the U.S., this use of CK has been largely replaced by the troponin test. However, the CK test may sometimes be used to help detect a second heart attack that occurs shortly after the first. (For more, see Common Questions #4.)

  • When is it ordered?

    A CK test may be ordered when muscle damage is suspected and at regular intervals to monitor for continued damage. It may be ordered when a muscle disease (myopathy) such as muscular dystrophy is suspected or when someone has experienced physical trauma, such as crushing injuries or extensive burns. The test may be ordered when a person has symptoms associated with muscle injury such as:

    • Muscle pain or aches
    • Muscle weakness
    • Dark urine (The urine may be dark because of the presence of myoglobin, another substance released by damaged muscles that can be harmful to the kidneys.)

    Testing may be ordered when a person has nonspecific symptoms, especially when taking a drug or after an exposure to a substance that has been linked with potential muscle damage.

  • What does the test result mean?

    A high CK, or a rise in levels in subsequent samples, generally indicates that there has been some recent muscle damage but will not indicate its location or cause. Serial test results that peak and then begin to drop indicate that new muscle damage has diminished, while increasing and persistent elevations suggest continued damage.

    Increased CK levels may be seen in some muscular disorders (myopathies), which have a wide variety of causes. People may have CK levels that are significantly to greatly increased, depending upon the severity of muscle damage. Those who have rhabdomyolysis may have CK levels that are 100 times normal levels and occasionally even higher.

    Increased CK may be seen with, for example:

    Normal CK levels may indicate that there has not been muscle damage or that it occurred several days prior to testing.

    Moderately increased CK levels may be seen following strenuous exercise such as in weight lifting, contact sports, or long exercise sessions.

  • Is there anything else I should know?

    People who have greater muscle mass have higher CK levels than those who don't; for this reason, men generally tend to have higher values than women.

    Any kind of muscle damage, including shots (injections), can temporarily increase CK.

    A low CK level may be seen in early pregnancy.

  • What is rhabdomyolysis?

    Rhabdomyolysis is the rapid breakdown of muscle tissue. This condition can be caused by serious physical, chemical, or biological injury to muscles. Examples of causes include:

    • Trauma, crushing injuries (e.g., car accidents, disasters such as earthquakes)

    • High-voltage electrical shock

    • Serious burns

    • Blood clot (thrombosis) that blocks blood flow

    Toxins (e.g., heavy metals, snake venom, carbon monoxide)

    • Infections (e.g., HIV, influenza, Streptococcus) — more common cause in children than adults

    • Inherited genetic and metabolic disorders that affect muscles' ability to get or use energy

    • Diseases such as muscular dystrophy and underlying conditions such as uncontrolled diabetes, hypothyroidism, and hyperthyroidism

    • Several drugs (examples include drugs of abuse (ethanol, cocaine), some antibiotics, antidepressants, corticosteroids, lithium, salicylates and statins)

    Complications can result from the rapid release of cell contents into the blood. This has been known to cause damage to kidneys (acute kidney injury, AKI) and disseminated intravascular coagulation (DIC). Once diagnosed and depending on the extent of injury, a person with rhabdomyolysis may be treated with intravenous fluids and other supportive care as well as procedures used to protect organs (e.g., dialysis to prevent/limit kidney damage).

  • Should everyone with muscle pain and weakness have a CK test?

    Muscle pain and weakness are common symptoms that are seen with many temporary conditions. General, routine CK testing is usually not required. However, if someone is taking a drug or has been exposed to a substance that has been linked with potential muscle damage and presents with muscle weakness, muscle aches, and/or dark urine, then CK testing may be indicated.

  • Is there anything I can do to lower my CK level?

    CK levels are a reflection of muscle damage. Temporary increases are seen with strenuous exercise but are not typically a concern unless severe or combined with extreme heat or humidity. An Increase in CK that is due to exposure to a toxin or a drug can be resolved by avoiding the toxin and/or potentially stopping taking the drug or changing therapy. You should not, however, stop taking a medication without first consulting with your healthcare provider. Increases in CK that are due to an underlying disease, such as uncontrolled diabetes or hypothyroidism, may resolve by controlling the condition.

  • Is the CK test used for purposes other than detecting skeletal muscle damage?

    The CK test was once one of the primary tests ordered to help diagnose a heart attack, but in the U.S., this use of CK has been largely replaced by the troponin test. However, the CK test may sometimes be used to help detect a second heart attack that occurs shortly after the first. A series of CK tests may be used to monitor heart damage to see if it resolves or continues.

    The heart damage that occurs during a heart attack can cause increased CK levels within a few hours. Levels peak within 12 to 24 hours and then return to normal within 2 to 4 days. If additional damage occurs or it is ongoing, such as during a second or subsequent heart attack, then CK levels may stay elevated.

    Sometimes, the CK test may be ordered when a heart attack is suspected and a troponin test is not available. In this case, when CK is elevated, a CK-MB test may be used as a follow-up test to determine whether the increase is due to heart damage or skeletal muscle damage.

    Chest pain and increased CK levels plus elevated CK-MB indicate that it is likely that a person has recently had a heart attack. Levels that drop, then rise again may indicate a second heart attack and/or ongoing heart damage.

View Sources

Sources Used in Current Review

2016 review performed by Hari Nair, PhD, DABCC, FACB, Technical Director, Boston Heart Diagnostics and the Editorial Review Board.

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