Creatine Kinase (CK)
- Also Known As:
- Total CK
- Creatine Phosphokinase
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.
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
A blood sample drawn from a vein in your arm
Test Preparation Needed?
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 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.
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:
- Recent crush and compression muscle injuries, trauma, burns, and electrocution
- Inherited myopathies, such as muscular dystrophy
- Hormonal (endocrine) disorders, such as thyroid disorders, Addison disease or Cushing disease
- Strenuous exercise
- Prolonged surgeries
- Infections – viral (such as influenza and HIV), bacterial, fungal, and parasitic (such as malaria)
- Connective tissue disorders (e.g. lupus, rheumatoid arthritis)
- Celiac disease
- Renal failure
- In critically ill patients
- High fever accompanied by shivering
- A blood clot (thrombosis) blocking the flow of blood
- Any drug or toxin that interferes with muscle energy production or increases energy requirements
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.
Health Professionals – LOINC
LOINC Observation Identifiers Names and Codes (LOINC®) is the international standard for identifying health measurements, observations, and documents. It provides a common language to unambiguously identify things you can measure or observe that enables the exchange and aggregation of clinical results for care delivery, outcomes management, and research. Learn More.
Listed in the table below are the LOINC with links to the LOINC detail pages. Please note when you click on the hyperlinked code, you are leaving Testing.com and accessing Loinc.org.
|LOINC||LOINC Display Name|
|2157-6||CK [Catalytic activity/Vol]|
|50756-6||CK (Bld) [Mass/Vol]|
Sources Used in Current Review
2016 review performed by Hari Nair, PhD, DABCC, FACB, Technical Director, Boston Heart Diagnostics and the Editorial Review Board.
(Update December 22, 2015) National Institute of Neurological Disorders and Stroke. Myopathy Information Page. Available online at http://www.ninds.nih.gov/disorders/myopathy/myopathy.htm. Accessed June 2016.
(Update 9/22/2015) Silberberg C. Rhabdomyolysis. MedlinePlus Medical Encyclopedia. Available online at https://www.nlm.nih.gov/medlineplus/ency/article/000473.htm. Accessed June 2016.
(January 31, 2000) Muscular Dystrophy Association. Simply Stated: The Creatine Kinase Test. Available online at https://www.mda.org/quest/article/simply-stated-the-creatine-kinase-test. Accessed June 2016.
Cabaniss, C.D. Creatine Kinase. H.W. Walker HK, Hurst JW. Clinical Methods: The history, Physical, and Laboratory Examinations. Boston: Butterworths; 1990. 32.
(December 27, 2015) Bethel C. Myopathies. Medscape Review. Available online at http://emedicine.medscape.com/article/759487-overview. Accessed June 2016.
Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.
Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp. 306-309.
MedlinePlus Medical Encyclopedia: CPK. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003503.htm. Accessed February 2009.
Zieve, D. (Updated 2012 September 14). Creatine phosphokinase test. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003503.htm. Accessed December 2012.
Junpaparp, P. et. al. (Updated 2012 November 28). Creatine Kinase. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/2074023-overview. Accessed December 2012.
Schreiber, D. and Miller, S. (Updated 2011 March 29). Use of Cardiac Markers in the Emergency Department. [On-line information]. Available online at http://emedicine.medscape.com/article/811905-overview. Accessed December 2012.
(© 1995-2012). Creatine Kinase (CK), Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8336. Accessed December 2012.
Lehman, C. and Meikle, A. (Updated 2012 November). Ischemic Heart Disease. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/IHD.html?client_ID=LTD. Accessed December 2012.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby’s Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 322-325.
Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 300-303.
McPherson, R. and Pincus, M. (© 2011). Henry’s Clinical Diagnosis and Management by Laboratory Methods 22nd Edition: Elsevier Saunders, Philadelphia, PA. Pp 439-440.
Dugdale, D. (Updated 2011 September 19). Rhabdomyolysis. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000473.htm. Accessed January 2013.
Bethel, C. (Updated 2012 March 9) Myopathies. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/759487-overview. Accessed January 2013.
Do, T. (Updated 2012 September 21). Muscular Dystrophy. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/1259041-overview. Accessed January 2013.
Eyal Muscal, E. and Morales DeGuzman, M. (Updated 2012 June 22). Rhabdomyolysis. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/1007814-overview. Accessed January 2013.
National Institute of Neurological Disorders and Stroke. NINDS Kennedy’s Disease Information Page. Available online at http://www.ninds.nih.gov/disorders/kennedys/kennedys.htm. Accessed November 2014.
Barkhaus, PE et al. Kennedy Disease Workup. Medscape. Available online at http://emedicine.medscape.com/article/1172604-workup. Accessed November 2014.
Better Health Channel. Kennedy’s disease. Available online at http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Kennedy’s_disease. Accessed November 2014.