What is Creatine Kinase?

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  • Written By: Jennifer Voight
  • Edited By: Jacob Harkins
  • Last Modified Date: 30 September 2019
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Creatine kinase, or CK, is an enzyme found mainly in the brain, heart, skeletal muscles, and other tissues. CK, also called as phosphocreatine kinase or CPK, helps cells produce a biochemical reaction that results in high-energy molecules that cells use to perform normal functions. When creatine kinase combines with adenosine triphosphate (ATP) it produces phosphocreatine and adenosine triphosphate (ATP). The muscles use these energy molecules to contract muscle fibers. This reaction may also work in reverse, so that phosphocreatine and ADP may create ATP.

There are three types of creatine kinase, or isoenzymes, produced by the body. CK-MM is produced by skeletal muscle, CK-MB is produced by the heart, and CK-BB is produced by the brain. Under certain circumstances, CK-MM may leak from cells and enter the bloodstream. This happens when muscle is damaged, either by muscular injury, exercise, or as a result of a neuromuscular disorder.

Doctors may test for the presence of creatine kinase in the blood to help diagnose and evaluate disease in which muscular degeneration may occur. A blood sample of serum is obtained and levels of CK measured in units of enzyme per liter. Levels typically vary depending on gender, activity levels and other factors, but a normal range is 22 to 198 units per liter.


High levels of creatine kinase can indicate neuromuscular disease such as muscular dystrophy. Elevated CK may also indicate heart attack, acute kidney failure, polymyosotis, dermatomyositis, hypothyroidism, hypothermia, recent surgery, or a recent session of vigorous exercise. In the case of neuromuscular disease, high levels of CK can diagnose the disease before the appearance of other symptoms.

In cases of rhabdomyolosis, muscles break down very quickly, releasing cellular contents into the bloodstream. When this happens, creatine kinase levels may soar very high, indicating a dangerous condition where types of proteins called myoglobins can enter the kidneys. Renal failure may result. Rhabdomyolosis is not a condition in and of itself, but a symptom of other conditions in the body. It most commonly happens after severe injury or as the result of medication and requires immediate medical attention.

People who take statins to control cholesterol may need to have CK levels monitored regularly. A side effect of statins is muscle pain and weakness that can, in rare cases, lead to rhabdomyolosis and risk of kidney failure. Close monitoring of creatine kinase levels can alert the doctor to early signs of muscle breakdown so kidney damage may be prevented.


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Post 3

Creatine supplements have nothing to do with CK enzymes, as the enzymes are released as a result of muscle damage. So you can't increase the enzymes by taking creatine because your body produces them. You don't inject them

Post 2

@snickerish - You are right, there is a supplement called creatine that many athletes use, in fact it has been called the most popular supplement by some. I don't know enough to be able to tell if there is a connection between the two.

I have known people in my life who have had loved ones who have had muscular dystrophy so I have heard a bit about creatine kinase and elevated levels as shown in the creatine kinase test. Elevated creatine kinase test would be levels that are of course *above* the normal range and the normal range of creatine kinase levels which are 22 to 198 U/L (units per liter) but theses numbers vary based on a number of factors such as gender and activity level.

Post 1

I had read about creatine or thought I had read about creatine as a supplement that was used by some professional athletes. Does this creatine supplement have something to do with creatine kinase?

And now that I know how important creatine kinase is, I wondered what is considered a high level of creatine kinase as found in a creatine kinase blood test?

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