What Is a Creatine Kinase and Why You Might Need a Test

Your body produces the enzyme creatine kinase or creatine phosphokinase to keep your muscles functioning properly. Healthcare providers use the creatine kinase (CK) test to check levels of this enzyme in your blood. You may have elevated creatine kinase levels for various reasons.

This article discusses the types of CK enzymes, why a healthcare provider might order a CK test, what it checks for, how the test works, and how the results are interpreted. 

Person with calf pain could have elevated creatine kinase due to rhabdomyolysis

Panuwat Dangsungnoen / EyeEm / Getty Images

What Is Creatine Kinase? 


Creatine kinase is an enzyme that’s responsible for healthy muscle function. When muscles break down, they release CK, elevating the protein levels in your blood.

Having a higher level of CK in your blood means you’ve experienced or are currently experiencing muscle damage.

Types of CK Enzymes 

There are three types of CK enzymes:

  • CK-MB: Elevated levels of this enzyme may signify heart muscle damage. 
  • CK-BB: Elevated levels of this enzyme may signify damage to the brain.
  • CK-MM: Elevated levels of this enzyme may signify skeletal muscle damage. 

What Is a CK Test Used For?

Healthcare providers order CK tests to check for muscle damage caused by diseases and injuries. 

Elevated CK levels might signify:

CK levels won’t always increase. For example, some diseases that affect the muscles may not cause elevated CK levels in the blood.

Common Symptoms of Muscular Disorders

Your healthcare provider might test for elevated CK levels to check for muscle damage if they suspect you have a muscular disorder.

Symptoms of muscular disorders can include:

  • Muscle weakness
  • Muscle stiffness
  • Muscle twitching
  • Numbness
  • Muscle spasms
  • Muscle pain
  • Cramping
  • Joint deformity

Why Do You Need a Test?

Reasons you might need a CK test:

  • Your healthcare provider suspects you have thyroid disease.
  • Your healthcare provider suspects you have a kidney issue.
  • Your healthcare provider suspects you have a muscle disorder.
  • You have muscle weakness, and your healthcare provider wants to find out if it’s muscle or nerve-related.
  • You have a diagnosed muscle disease, and your healthcare provider wants to check how it's progressing.
  • You recently had a stroke (a blockage of blood flow or bleeding in the brain).
  • You’re having chest pain or other heart attack symptoms.
  • You’re taking statins (medications used to lower cholesterol) and experiencing side effects.

Most healthcare providers now test for elevated cardiac troponin levels, another protein, instead of the CK-MB test when testing for signs of a heart attack.

What Is Rhabdomyolysis?

Rhabdomyolysis (rhabdo) happens when damaged muscles break down and release their contents into your bloodstream.

Signs you're experiencing rhabdo may include:

  • Severe muscle cramping
  • Severe weakness
  • Dark-colored urine

You may also have no symptoms at all.

You're more likely to develop rhabdo if you:

  • Have a physically strenuous job
  • Take certain substances like cocaine
  • Use supplements
  • Drink in excess
  • Take certain medications
  • Have an infection
  • Have certain chronic conditions like muscular dystrophy

During rhabdomyolysis, CK levels will typically be extremely high.

What Happens During the Test

The CK test requires a simple blood sample. A healthcare professional will draw blood from a vein and send the sample to the laboratory for testing.

Your healthcare provider may need to perform the test multiple times since the CK levels don’t immediately increase.

Before the Test

It’s a good idea to avoid physical activity before getting a CK test. That’s because exercise can cause muscle damage and may lead to an elevated level.

Risks

Risks of getting your blood drawn for a CK test are minimal but may include:

  • Infection due to improper sanitary practices
  • Bleeding
  • Slight pain during the procedure
  • Soreness and bruising after the blood draw
  • Lightheadedness

What Results Mean 

A CK test doesn’t provide a diagnosis. But it does give the healthcare provider clues to form a diagnosis or order further testing.

Elevated levels of CK signify muscle damage. More specifically:

  • Elevated levels of CK-MB can mean you have some sort of heart damage.
  • Elevated levels of CK-MM can mean you have skeletal muscle damage, which may be due to a muscular disease or acute injury.
  • Elevated levels of CK-BB can mean you have some kind of brain injury or have recently had a stroke.

Laboratories may have different reference ranges for CK, so your results should be interpreted based on their reported reference range. One such CK range for adults is between 22 to 198 units per liter (U/L). What’s normal for you can vary depending on your activity levels, sex, and race.

Your healthcare provider will likely order more tests to make a diagnosis since CK levels alone won’t provide a complete picture of your condition.

Summary 

The creatine kinase test is a blood test that checks whether the CK levels in your blood are elevated. Elevated CK levels can mean you have some sort of muscle damage in your body. It doesn’t provide a full picture of your health, so healthcare providers typically perform other tests to make a diagnosis. 

A Word From Verywell 

Before you go for any blood test, it’s a good idea to tell your healthcare provider about any medications or supplements you’re taking. Some medications, supplements, and vitamins can impact CK levels in your blood, potentially affecting the result. 

Frequently Asked Questions

  • Should high levels of creatine kinase concern you?

    Not necessarily. Typical results can fall into a wide range and vary depending on your sex or race. Physical activity and certain medications can also raise levels. High levels are a starting point in the diagnostic process. Your healthcare provider will order more tests to determine why you have specific symptoms. 

  • What causes your CK levels to go up?

    Several things can elevate your CK levels, including medication and strenuous exercise. Muscle damage can also cause levels to rise.

  • What is the treatment for high levels of creatine kinase?

    Treatment will depend on the underlying condition causing the elevated levels. 

  • What foods should you avoid with a high creatine kinase?

    Again, this depends on the underlying condition causing your high levels. If you have high CK levels because of kidney failure, your healthcare provider may recommend a change in diet. 

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5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Muscular Dystrophy Association. Simply stated: the creatine kinase test

  2. University of Rochester Medical Center. Creatine kinase (blood)

  3. MedlinePlus. Creatine kinase

  4. Beaumont. Neuromuscular disorders.

  5. Centers for Disease Control and Prevention (CDC). Rhabdomyolosis.