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  • Also Known As:
  • CK MB
  • CPK MB
  • Formal Name:
  • Creatine Kinase-MB
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At a Glance

Why Get Tested?

To distinguish between skeletal muscle and heart muscle damage; sometimes to determine if you have had a heart attack (if the troponin test is not available); sometimes to detect a second or subsequent heart attack or to monitor for additional heart damage

When To Get Tested?

When you have an increased creatine kinase (CK) level and the health care practitioner wants to determine whether it is due to skeletal or heart muscle damage; when it is suspected that you have had a second heart attack or have ongoing heart damage

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?


You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Testing.com. 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.

Testing.com 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-MB (CK-MB) is a form of an enzyme found primarily in heart muscle cells. This test measures CK-MB in the blood.

CK-MB is one of three forms (isoenzymes) of the enzyme creatine kinase (CK). These isoenzymes include:

  • CK-MM (found in skeletal muscles and the heart)
  • CK-MB (found mostly in the heart, but small amounts found in skeletal muscles)
  • CK-BB (found mostly in the brain and smooth muscle, such as the intestines and uterus)

CK is released from muscle cells and is detectable in the blood whenever there is muscle damage. The small amount of CK that is normally in the blood is primarily CK-MM. CK-BB almost never gets into the blood, and CK-MB will typically only be present in significant amounts when the heart is damaged. A CK test measures the total level but does not distinguish between the three isoenzymes. When there is an increased amount of CK present in the blood, the CK-MB test can be used to determine whether it is due to heart damage or is more likely to be related to skeletal muscle injury.

Common Questions

How is it used?

A creatine kinase-MB (CK-MB) test may be used as a follow-up test to an elevated creatine kinase (CK) in order to determine whether the increase is due to heart damage or skeletal muscle damage. The test is most likely to be ordered if a person has chest pain or if a person’s diagnosis is unclear, such as if a person has nonspecific symptoms like shortness of breath, extreme fatigue, dizziness, or nausea.

CK and CK-MB were once the primary tests ordered to detect and monitor heart attacks, but they have now been largely replaced by the troponin test, which is more specific for damage to the heart.

Sometimes, the CK test may be used if 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.

When is it ordered?

CK-MB is usually ordered along with or following an elevated total CK when a person has chest pain and a healthcare practitioner wants to determine whether the pain is due to a heart attack. It is typically ordered for this purpose when the more specific troponin test is not available. A CK-MB may also be ordered when a person has a high CK to determine whether the muscle damage detected is to the heart or other muscles.

Increased CK-MB can usually be detected in someone with a heart attack about 3-6 hours after the onset of chest pain. The level of CK-MB peaks in 12-24 hours and then returns to normal within about 48-72 hours. If there is a second heart attack or ongoing damage, then levels may rise again and/or stay elevated longer.

What does the test result mean?

CK-MB is normally undetectable or very low in the blood.

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.

If CK-MB is elevated and the ratio of CK-MB to total CK (relative index) is more than 2.5-3, then it is likely that the heart was damaged. A high CK with a relative index below this value suggests that skeletal muscles were damaged. (For more, see Common Questions #3.)

Any kind of heart muscle damage can cause an increase in CK and CK-MB, including physical damage from trauma, surgery, inflammation, and decreased oxygen (ischemia). Strenuous exercise may also increase both CK and CK-MB, but usually with a lower relative index.

Kidney failure can cause a high CK-MB level.

Rarely, chronic muscle disease, low thyroid hormone (T3, T4) levels, and alcohol abuse can increase CK-MB.

Is there anything else I should know?

Since CK-MB is also present in small quantities in skeletal muscle, significant damage to skeletal muscles can also increase the CK-MB level. If both skeletal and heart muscles are damaged, the presence of CK-MB due to a heart attack could be masked.

If I have chest pain, does that mean I am having a heart attack?

Many other problems can cause chest pain, and it is not always possible to tell just from the type of chest pain whether or not you are having a heart attack. Many people have chest pain from straining the muscles in their chest, and chest pain can occur with some lung problems. Chest pain can be a warning sign of hardening of the arteries of the heart (coronary artery disease or CAD). Chest pain that occurs during exercise, hard work, or at times of stress, lasts for a few minutes and goes away with rest is called angina. If the pain lasts longer than just a few minutes, especially if it occurs when you are resting, seek immediate medical attention.

What other tests detect a heart attack?

Health care practitioners may use more than one test to determine if a person who has chest pain is having a heart attack. Troponin is generally considered the most accurate test. Besides CK-MB, a CK test and a myoglobin test may be performed, although they are less specific as other conditions can also produce an increase in these two tests.

What is CK index?

People with skeletal muscle damage may have elevated CK-MB levels. To help differentiate heart attack from skeletal muscle damage, a CK index can be calculated using CK-MB and total CK as follows: CK index = (CK-MB, ng/mL) x100 / (total CK activity, IU/L). If CK-MB is elevated and the CK index in higher than 2.5 to 3.0, heart damage is likely.

View Sources

Sources Used in Current Review

2017 review performed by Jagannadha Rao Peela, MD.

Kemp M, et al. Biochemical markers of myocardial injury. Br J Anaesth 2004; 93: 63±73. Available online at http://bja.oxfordjournals.org/content/93/1/63.full.pdf. Accessed January 2017.

Koenig K. Absolute CK-MB vs. CK-MB Relative Index for Cardiac Risk Stratification. Journal Watch. 2003;2(7). Available online at http://www.medscape.com/viewarticle/459702. Accessed January 2017.

(January 13, 2017) Chest Pain. NHS Choices. Available online at http://www.nhs.uk/conditions/chest-pain/Pages/Introduction.aspx. Accessed January 2017.

(June 22, 2015) What is a Heart Attack? National Heart, Lung and Blood Institute. Available online at https://www.nhlbi.nih.gov/health/health-topics/topics/heartattack/diagnosis. Accessed January 2017.

©2016 Vitros. Ortho-Clinical Diagnostics. CK-MB. Available online at https://www.cmmc.org/cmmclab/IFU/CKMB_GEM1300_WW_EN_I.pdf. Accessed January 2017.

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. 312-315.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER and Bruns DE, eds. 4th ed. St. Louis, Missouri: Elsevier Saunders; 2006. P. 599.

Engel G, Rockson SG. Rapid diagnosis of myocardial injury with troponin T and CK-MB relative index. Mol Diagn Ther. 2007;11(2): 109-16. Available online through http://www.ncbi.nlm.nih.gov/pubmed. Accessed February 2009.

Innotrac Diagnsostics. CK-MB Kit. Available online at http://www.innotrac.fi/index.php?main=products&section=cardiac&subsection=ckmb. Accessed February 2009.

Dugdale, D. (Updated 2011 February 17). CPK isoenzymes test. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003504.htm. 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.

Domanski, M. (2012 December 03). Prognostic Implications of Troponin T and Creatine Kinase, MB Elevation After Coronary Artery Bypass Grafting. Medscape Today News from Am Heart J. v 164(5):636-637. [On-line information]. Available online at http://www.medscape.com/viewarticle/774259. Accessed December 2012.

(© 1995-2012). Creatine Kinase (CK) MB Isoenzyme, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/82429. 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 489.


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