Creatine kinase (CK)

What it measures

CK is an enzyme found mainly in skeletal muscle, heart and brain. Total CK is used to detect muscle injury, rhabdomyolysis, myositis and statin-related myopathy.

Specimen and preparation

• Specimen: Serum or lithium-heparin plasma
• Tube: Gold top
• Preparation: Avoid strenuous exercise and intramuscular injections for 24–48 hours before testing.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Rhabdomyolysis and crush injury
• Intense exercise, IM injections, seizures
• Myositis and muscular dystrophy
• Statin myopathy
• Myocardial infarction
• Hypothyroidism

Causes of low values

• Low muscle mass
• Prolonged bed rest

Method

Kinetic UV assay (IFCC, N-acetylcysteine activated)

Good to know

Levels over 5× the upper limit suggest rhabdomyolysis; check potassium, creatinine and urine myoglobin. Baseline CK is higher in people of African ancestry.

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