CPK (Creatine Phosphokinase) Test

A CPK test is performed when muscle damage is expected or when a person shows apparent symptoms of a muscle injury, such as

• Muscle aches or pain
• Muscular weakness
• Restricted muscle movements
• Muscle spasms
• Muscle soreness
• Dark-coloured urine (urine turns darker due to the presence of myoglobin, a substance released by damaged muscles, which can affect kidneys)

This test is also performed at regular intervals for monitoring continual damage. Furthermore, it is useful for diagnosing myopathies, such as muscular dystrophy and trauma such as burns or crush injuries.

CPK has three isoenzymes present in different locations, which helps in determining the precise area of the damage:

• CPK-MB (found in the heart muscle)
• CPK-MM (found in the skeletal muscle)
• CPK-BB (found in the brain)

No special preparations are needed for this test.

An experienced laboratory specialist will collect a blood sample from a vein in your arm by inserting a small needle. A small quantity of blood will be withdrawn into a sterile vial or a test tube, which will be capped properly and sent to a lab for analysis.

You may feel a momentary pricking pain when the needle goes into the vein. Apart from that, there is a minimal risk of pain, light-headedness and bruising at the site of injection. However, at most times, these symptoms disappear quickly. Rarely, an infection may occur at the blood withdrawal site. Make sure to check in with your doctor if the symptoms persist.

CPK levels are expressed as micrograms per litre (mcg/L).

Normal results: Normal levels of CPK range from 10 to120 mcg/L.

Abnormal results: 

High levels of CPK are seen in case of:

• Recent injury or trauma (burns, crush injuries or electrocution)
• Muscular dystrophy
• Strenuous exercise
• Brain injury or stroke
• Delirium tremens
• Polymyositis
• Prolonged surgeries
• Endocrine disorders (thyroid disease, Addison disease or Cushing disease)
• Seizures
• Connective tissue disorder (rheumatoid arthritis, systemic lupus erythematosus [SLE])
• Celiac disease
• Viral, bacterial or parasitic infections
• Kidney failure
• Fever with chills or shivering
• Thrombosis (blood clot in a blood vessel)

A moderately high level of CPK is seen during or after strenuous exercises, after a prolonged workout session or after a sport session.

People having greater muscle mass are known to have high levels of CPK; thus, males have relatively higher levels over females. Any injury to muscles, such as taking an injection, can temporarily raise CPK levels. During early pregnancy, CPK levels tend to be on the lower side.

CPK was once used primarily to diagnose heart attacks, but it is now replaced by troponin level evaluation; however, it is still used to diagnose a heart attack that occurs immediately after the first one.

CPK is usually evaluated along with certain other tests, including electrolyte levels, blood urea nitrogen (BUN), creatinine levels and urine myoglobin levels (when rhabdomyolysis is suspected)

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.