Creatine Kinase (CK): What It Is, Purpose & Procedure (2024)

What is creatine kinase (CK)?

Creatine kinase (CK) is an enzyme that mainly exists in your heart and skeletal muscle, with small amounts in your brain. The cells in your skeletal muscles, heart muscles or brain release creatine kinase into your blood when they’re damaged.

An enzyme is a protein that acts as a catalyst to bring about a specific biochemical reaction.

The small amount of CK that’s normally in your blood mainly comes from your skeletal muscles (the muscles that are attached to your bones and tendons). Any condition, injury or event that causes muscle damage and/or interferes with muscle energy production or use increases levels of CK in your blood. For example, intense exercise can increase CK levels. Muscle diseases (myopathies) such as muscular dystrophy can also increase CK levels.

There are three types of CK enzymes:

• CK-MM: Found mostly in your skeletal muscles.
• CK-MB: Found mostly in your heart muscle.
• CK-BB: Found mostly in your brain tissue.

What is a creatine kinase (CK) test?

A creatine kinase (CK) test measures the amount of creatine kinase in your blood.

Elevated CK levels may indicate skeletal muscle, heart or brain damage or degeneration — either chronic (long-term) or acute (short-term).

Other names for a creatine kinase test include:

• CK total.
• CK creatine.
• Phosphokinase CPK.

What is the function of creatine kinase (CK)?

The regular function of creatine kinase (CK) is not really related to what elevated levels of it may indicate in a blood test. CK’s job is to add a phosphate group, a group of natural chemicals, to creatine, a substance in your muscle cells that helps your muscles produce energy. When CK adds phosphates to creatine, it turns the creatine into the high-energy molecule, phosphocreatine, which your body uses to generate energy.

CK gets into your bloodstream when your muscles, heart or brain experience acute damage or chronic degeneration. When your muscles are damaged, the muscle cells break open, and their contents, including creatine kinase, leak into your bloodstream.

What are creatine kinase (CK) tests used for?

Healthcare providers most often use creatine kinase (CK) tests to diagnose and monitor the following muscle issues:

• Muscular diseases.
• Muscular injuries.
• Muscular inflammation (myositis).

Since muscle-related symptoms can be symptoms of several different conditions, your provider may order other tests along with a CK test, including:

• Electrolytes.
• BUN (blood urea nitrogen).
• Creatinine.
• Urine myoglobin.

Muscular diseases

Muscular diseases (myopathies) include:

• duch*enne muscular dystrophy (DMD): This is a rare inherited condition that causes weakness, breakdown and loss of function of your skeletal muscles. It most commonly affects people assigned male at birth.
• Rhabdomyolysis: This condition involves a rapid breakdown of your muscle tissue. It can be caused by a serious injury, muscle disease or other condition.

Muscular injuries

Muscular injuries can result from the following situations:

• Crushed, compressed, torn or strained muscles from accidents or intense exercise.
• Third-degree burns.
• Electrocution.

Muscular inflammation

Types of muscular inflammation (myositis) include:

• Polymyositis: This inflammatory muscle disease causes muscle weakness, usually in the muscles closest to the trunk of your body.
• Dermatomyositis: This is a rare condition that causes muscle weakness and a skin rash.
• Pyomyositis: This is a rare bacterial infection of the muscle that often forms an abscess.

Creatine kinase tests and heart attacks

Healthcare providers sometimes use a creatine kinase (CK) test to help diagnose a heart attack, though not very often. CK testing used to be a common test for heart attacks, but healthcare providers now use another test, called troponin, which is better at detecting heart damage.

Why do I need a creatine kinase (CK) test?

Your healthcare provider may order a creatine kinase (CK) test for you if you have symptoms of a muscular disorder, which include:

• Muscle pain and/or cramps.
• Muscle weakness.
• Balance issues.
• Numbness or tingling.
• Dark urine (pee).

Your provider may also order this test if you’ve had a muscle injury or stroke. CK levels may not peak until up to two days after certain injuries, so you may need to do the test more than once.

Who performs a creatine kinase (CK) test?

A healthcare provider called a phlebotomist usually performs blood draws, which include those for a creatine kinase (CK) blood test, but any healthcare provider who is trained in drawing blood can perform this task. They then send the samples to a lab where a medical laboratory scientist prepares the samples and performs the tests on machines known as analyzers.