Blood draw
Creatine Kinase (CK)
CK; muscle damage or exertion.
€ 32,00
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Muscles and bones · Blood
Creatine kinase (CK)
An enzyme from the muscles that rises in the blood with muscle damage; often temporarily very high after heavy exercise.
At a glance
- Measured in blood
- In 3 test panels
- No special preparation
Explanation
Creatine kinase (CK): what is measured?
Creatine kinase (CK) is an enzyme found mainly in the skeletal muscles and the heart muscle that helps supply energy to muscle cells. Normally only a small amount enters the blood, mostly from the skeletal muscles. If muscle cells are damaged, by exercise, an injury or a muscle disease, more CK enters the blood. How high the value is also depends on muscle mass, sex and training.
What can it detect?
- Muscle damage after heavy or unusual exercise
- Muscle symptoms as a side effect of statins (cholesterol-lowering drugs)
- Muscle diseases, such as muscle inflammation (myositis) or muscular dystrophy
- Severe muscle breakdown (rhabdomyolysis)
Result
What does the result mean?
Creatine kinase (CK) too high
A raised CK is very often caused by exercise. According to the Dutch Society for Clinical Chemistry (NVKC), the value can rise considerably after hard training, a (half) marathon or the Nijmegen Four Days Marches, and the less trained someone is, the larger the rise; CK can then stay raised for days, sometimes up to many times the upper limit, without anything being wrong. A fall, a muscle injury, an injection into a muscle and a lot of muscle mass also give a higher value. CK can rise with the use of statins, usually together with muscle pain; according to the Dutch medical specialists' guideline (FMS), most muscle symptoms with statins do not come with a clear rise in CK, and a severe rise is rare. Other causes are an underactive thyroid, a lot of alcohol, muscle inflammation, inherited muscle diseases and a heart attack, which comes with symptoms such as chest pain. Dark, cola-colored urine with muscle pain and weakness after extreme exercise may point to severe muscle breakdown and needs prompt assessment.
Creatine kinase (CK) too low
A low CK usually has no meaning. It occurs with little muscle mass, in older people and in people who move little. A low value is not used to diagnose a disease.
After an abnormal result
With a raised CK, the GP asks about exercise, injuries, medicines and symptoms, and usually repeats the measurement after a period of rest. In statin users with muscle symptoms and a raised CK, the GP assesses whether the statin is temporarily stopped or replaced, according to the Dutch GP guideline (NHG) on cardiovascular risk management. If CK stays raised without explanation, further blood tests may follow (including thyroid function and kidney function) and possibly a referral to a neurologist.
Reliability
How reliable is the test?
The CK measurement is accurate, but a raised value in someone who exercises is hard to interpret, because exercise in the days before strongly affects the result. In statin users without muscle symptoms CK says little, because most muscle symptoms with statins do not come with a clear rise in CK and a severe rise is rare; the value is mainly informative with muscle symptoms that may point to a side effect. For diagnosing a heart attack, another marker (troponin) says more than CK. An abnormal value is therefore assessed together with symptoms, training and medicines, and repeated if in doubt after a number of days without heavy exercise.
What can affect the result?
- Heavy or unusual exercise, strength training, long-distance running and muscle injuries raise CK for up to several days after the exercise.
- Statins and some other medicines can raise CK; a normal CK does not rule out a statin side effect.
- An injection into a muscle, a fall or surgery in the days before the sample collection raise the value.
- The reference values differ by laboratory, sex and ethnic background; people with a lot of muscle mass or a dark skin color often have a higher normal value.
Who it is for
Who is the test useful for?
Useful for
Useful with unexplained muscle pain, muscle weakness or dark urine, with muscle symptoms during statin use and when a muscle disease is suspected. After a period of illness with persistent muscle symptoms, CK can also help rule out muscle damage. In athletes, the result can only be interpreted if there has been no heavy training for several days. In healthy adults without symptoms, and in statin users without muscle symptoms, a raised value says little and is often caused by exercise.
How common is it?
A raised CK after heavy exercise is very common in athletes. Muscle symptoms with statin use are reported in practice by a large share of users, but according to the Dutch medical specialists' guideline (FMS), a severe rise in CK occurs in fewer than 1 in 1,000 to 10,000 users per year. Muscle diseases such as myositis and muscular dystrophy are rare.
FMS guideline on inherited dyslipidemia: statin-related side effects; NVKC, allesovertesten.nl
Drawbacks and risks
- A raised CK after exercise is common and, without a repeat test after rest, can lead to unnecessary worry or unnecessary follow-up tests.
- A raised CK without symptoms can lead to unnecessarily stopping a statin, while the statin lowers the risk of cardiovascular disease.
Get tested
Creatine kinase (CK): test panels
Creatine kinase (CK) is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
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