At a Glance
Why Get Tested?
To detect and monitor muscle damage; to help diagnose conditions associated with muscle damage; sometimes to help determine if you have had a heart attack, although for heart attack detection, this test has been largely replaced by troponin
When to Get Tested?
When you have muscle weakness, muscle aches, and/or dark urine and your health practitioner suspects muscle damage; sometimes to monitor for muscle injury resolution or persistence; sometimes to detect ongoing or additional heart damage after a heart attack
A blood sample drawn from a vein in your arm
Test Preparation Needed?
The Test Sample
What is being tested?
This test measures the amount of creatine kinase (CK) in the blood. Creatine kinase 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.
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, inflammation of muscles, called myositis, can increase CK. Rhabdomyolysis, a breakdown of skeletal muscle tissue, is associated with significantly elevated levels of CK.
Rhabdomyolysis and increased CK may be seen with, for example:
- Crush and compression muscle injuries, trauma, burns, and electrocution
- Prolonged surgeries
- Intense physical exertion, especially in heat and humidity and when dehydrated
- Infections – viral (such as influenza and HIV), bacterial, fungal, and parasitic (such as malaria)
- A blood clot (thrombosis) blocking the flow of blood
- Any drug or toxin that interferes with muscle energy production or increases energy requirements
Damage to muscles, such as 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, then CK levels may stay elevated. This fact makes the CK test potentially useful for monitoring for continuing heart or other muscle damage.
How is the sample collected for testing?
A blood sample is taken by needle from the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
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 through http://emedicine.medscape.com. 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 through http://emedicine.medscape.com. 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 through http://www.mayomedicallaboratories.com. 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 through http://www.arupconsult.com. 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 through http://emedicine.medscape.com. 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 through http://emedicine.medscape.com. 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 through http://emedicine.medscape.com. 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 through http://www.ninds.nih.gov. Accessed November 2014.
Barkhaus, PE et al. Kennedy Disease Workup. Medscape. Available online at http://emedicine.medscape.com/article/1172604-workup through http://emedicine.medscape.com. 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 through http://www.betterhealth.vic.gov.au. Accessed November 2014.
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.