Felis ISSN 2398-2950

Blood biochemistry: creatinine phosphokinase

Synonym(s): CPK, CK

Contributor(s): Kathleen P Freeman, Jane Miller


  • Occurs as 3 isoenzymes in skeletal muscle, cardiac muscle and central nervous system (CNS):
    • CK1 (BB) in brain, peripheral nerve, cerebrospinal fluid and viscera. Not found in serum.
    • CK2 (MB) in cardiac muscle; very small amounts in skeletal muscle.
    • CK3 (MM) in skeletal and cardiac muscle.
  • Separation of CK isoenzymes has not yet been found to be of any greater diagnostic significance than total serum CK activity.
  • Most sensitive indicator of muscle damage.
  • CK has short half-life.
  • Levels peak 6-12 hours post-injury, returning to normal in 2-3 days after cessation of injury. Persistent elevation indicates continuing or active disease.


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  • Methods (and reference interval) vary between laboratories.
  • Enzymatic/spectrophotometric measurement.


  • Routine test.



  • This is an extremely sensitive test for muscle damage.
  • As a result, only large increases or persistent moderate increases may be of clinical significance.


  • Poor specificity for disease processes.

Technician (extrinsic) limitations

  • Routine test.

Result Data

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Further Reading


Refereed papers

  • Recent references from VetMedResource and PubMed.
  • Grevel V, Opitz M, Steeb C and Skrodzki M (1993) Myopathy due to potassium deficiency in eight cats and a dog. Berl Munch Tierarztl Wochenschr 106(1), 20-26.
  • Leon A, Bain S A and Levick W R (1992) Hypokalemic episodic polymyopathy in cats fed a vegetarian diet. Aust Vet 69(10), 249-254.

Other sources of information

  • Ettinger S J & Feldman E C (eds) (2000) Textbook of Veterinary Internal Medicine. 5th edn. Philadelphia: W B Saunders & Co.
  • Kaneko J J, Harvey J W & Brass M L (eds) (1997) Clinical Biochemistry of Domestic Animals. 5th edn. Boston: Academic Press.
  • Duncan J R, Prasse K W & Mahaffey E A (1994) Veterinary Laboratory Medicine. Clinical Pathology. 3rd edn. Iowa: Iowa University Press.