Also Known As
Creatine Phosphokinase (CPK)
Formal Name
Creatine Kinase
This article was last reviewed on
This article waslast modified on 9 March 2020.
At a Glance
Why Get Tested?

To detect and monitor muscle damage and to help diagnose conditions associated with muscle damage

When To Get Tested?

If you have muscle aches or pain, tenderness, weakness and swelling after muscle damage, particularly if your urine becomes dark reddish-brown in colour

Sample Required?

A blood sample taken from a vein in the arm

Test Preparation Needed?


On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

This test measures the amount of creatine kinase (CK) in the blood. CK is an enzyme found in the heart muscle, brain tissue, skeletal muscle and other tissues. Increased amounts are released into the bloodstream when there is muscle damage. CK occurs in three major forms, called isoenzymes:

  • CK-MB (found mostly in heart muscle)
  • CK-BB (found mostly in brain tissue)
  • CK-MM (found in skeletal muscles)
Accordion Title
Common Questions
  • How is it used?

    The small amount of CK that is normally present in the blood comes primarily from skeletal muscles. Conditions that cause muscle damage may lead to an increase in blood CK. For example, inflammation of muscles, called myositis, can increase CK concentrations.

    Rhabdomyolysis, a severe breakdown of skeletal muscle tissue that causes muscle pain, tenderness, weakness and swelling, is associated with significantly elevated levels of CK, often 100 times normal. Measurement of CK is used to assess the extent of muscle damage and to monitor its progress.

    Measurement of CK is often used for the assessment of muscle related side effects from drugs such as statins and as part of the investigation of patients with suspected muscular dystrophy.

  • When is it requested?

    Measurement of CK is requested in people who have sustained severe muscle trauma, particularly from crush injuries, burns or electrocution, and are likely to develop rhabdomyolysis.

    CK may also be requested in those who develop symptoms or signs of less severe muscle damage

    • after being immobile for a long time on a hard surface, for example during an operation or after a stroke, drugs or alcohol
    • following very severe exercise
    • after a fit
    • during a severe infection
    • while taking certain medicines, for example a statin to lower cholesterol

    Rhabdomyolysis is likely if the urine develops a reddish-brown colour and gives a positive dip-stick test for blood. (Myoglobin, a red protein released from damaged muscle, reacts with the dip-stick in the same way as haemoglobin from blood cells.) The excretion of myoglobin by the kidney can potentially cause kidney failure.

    Blood concentrations of CK (or its CK-MM isoenzyme) are also requested as a first step in the diagnosis of muscular dystrophy in infants or children who

    • have difficulty walking
    • have difficulty standing
    • have difficulty lifting weights
    • need help climbing stairs

    The test may subsequently be used to screen family members.

  • What does the test result mean?

    A high CK concentration, or a result that goes up from the first to a second or later samples, generally indicates that there has been some recent muscle damage. Serial test results that peak and then begin to drop indicate that new muscle damage has diminished, while increasing and persistent elevations suggest continuing damage.

  • Is there anything else I should know?

    For the detection of heart muscle damage, myocardial infarction, changes in serum CK and its heart tissue (MB) isoenzyme have been largely replaced by the more heart specific nonenzymatic markers, cardiac troponin I or T.

    People who have greater muscle mass have higher normal CK levels. For example, a young fit male will have more muscle mass than an elderly female and hence a higher CK concentration. Normal exercise such as running or cycling and drug injections into muscle can increase CK concentrations.

    CK concentrations have been found to be normally higher in black race populations.

  • How does the myoglobin that is released from muscle with CK during rhabdomyolysis produce renal failure?

    Myoglobin released from damaged muscle into plasma is filtered by the kidneys into the urine but can precipitate in the kidney tubules, obstructing urine formation. This is a particular risk if shock lowers blood pressure and reduces the rate of urine production.

  • Do all patients with muscular dystrophy have raised plasma CK values?

    No, there are many different types of muscular dystrophy, some without raised CKs.
    Raised CK values are usually found during the active phase of muscular dystrophy.