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CK (Creatinine Kinase)

Creatinine Kinase (CK, CPK) is an enzyme found primarily in the heart and skeletal muscles, and to a lesser extent in the brain. Significant injury to any of these structures will lead to a measurable increase in CK levels.

Elevations found in:

  • Myocardial infarction
  • Crushing muscular trauma
  • Any cardiac or muscle disease, but not myesthenia gravis or multiple sclerosis
  • Brain injury
  • Hypothyroidism
  • Hypokalemia
  • Once elevated, CK remains elevated for several days, if the injury is acute. 
  • If there is on-going injury, the CK will remain elevated indefinitely.


  • In acute MI, CK usually rises faster than SGOT and returns to normal faster than the SGOT.

CK/CPK Isoenzymes

There are three Isoenzymes. Measuring them is of value in the presence of elevated levels of CK or CKP to determine the source of the elevation.

Isoenzyme MM BB MB
Synonym CK3 CK1 CK2
Found in: Skeletal M.
Heart M.
GI Tract
GU Tract
Heart M.
  • Normal levels of CK/CPK are almost entirely MM, from skeletal muscle.
  • Elevated levels of CK/CPK resulting from acute myocardial infarction are about half MM and half MB

Normal Values for CK, CPK*

Men 5-100 IU/L


10-70 IU/L
Pregnancy 5-40 IU/L

Normal Values for CK or CPK Isoenzymes*

MM 97%-100% 


BB 0%

*These are general values taken from a variety of sources. The actual normal values may vary from lab to lab and from one type of testing protocol to another.




Source: Operational Medicine 2001,  Health Care in Military Settings, NAVMED P-5139, May 1, 2001, Bureau of Medicine and Surgery, Department of the Navy, 2300 E Street NW, Washington, D.C., 20372-5300