• Elevated CK warrants prompt referral to neurology. In many specialty clinics, an elevated CK level reduces wait time for consultation. (A personal phone call may also be helpful.)
• Normal CK does not rule out neuromuscular disease. Referrals to specialists, physical therapy, and early intervention are warranted for a child with motor delay, even with normal CK levels.
• A mildly elevated CK (1-2x normal) should be followed up. Repeat the test after several weeks, and if you have concerns, consult with a neurologist.

The amount of CK in the serum is reported in units (U) of enzyme activity per liter (L) of serum. In a healthy adult, the serum CK level varies with a number of factors (gender, race and activity). The normal range is generally up to 250 U/L (units per liter) but varies by laboratory.

CK levels can be mildly elevated (~500 U/L) in neuropathies like Charcot-Marie-Tooth disease or spinal muscular atrophy, or grossly elevated (~3,000 to >30,000 U/L) in Duchenne muscular dystrophy or some other muscular dystrophies.

Mildly elevated CK (<500) should be repeated in several weeks as it could be temporarily elevated as a result of self-limited conditions such as recent immunization, muscle trauma, or viral infection.

During episodes of acute muscle breakdown (i.e., rhabdomyolysis), CK levels can temporarily go off the scale, topping out at 50,000 to 200,000 U/L. This is a medical emergency and patients should be referred to the nearest Emergency Department immediately.

CK levels do not reflect the level of functional impairment.