How is it used?
Your doctor may request the measurement of CK if they suspect you have muscle damage. Blood levels of CK rise when any muscle cell is damaged. Once the damage stops, the level of CK in the blood starts to go down to normal. The blood level of CK may also rise in a person having a heart attack. A heart attack is a very sudden form of damage to the muscle of the heart, so the CK is released from the damaged heart muscle cells quickly. After a heart attack, the level of CK in the blood will rise within a few hours and go back to normal in a few days.
When is it requested?
It can be requested if your doctor suspects any type of muscle damage causing pain or weakness. The test used to be used for people suspected of having a heart attack, but now better tests are used, such as tests for the form of CK known as CK-MB, or one of the troponin tests.
What does the test result mean?
A high CK level in the blood usually means there has been damage to muscle which has made the muscles release CK into the blood. There are many possible causes for this. The heart is a muscle too, and when it is damaged in a heart attack it releases CK into the blood. However, there are better blood tests for heart attack now, such as the form of CK known as CK-MB or one of the troponin tests.
Male (18-60 years) 45 – 250 U/L
Male (60 -120 years) 40 – 200 U/L
Female 30 – 150 U/L
The reference intervals shown above are known as a harmonised reference interval. This means that eventually all laboratories in Australia will eventually use this same interval so wherever your sample is tested, the reference interval should be the one shown above. Laboratories are in the process of adopting these harmonised intervals so it is possible that the intervals shown on the report of your results for this test may be slightly different until this change is fully adopted. More information can be found under Reference Intervals – An Overview.
Is there anything else I should know?
Natural wear and tear will cause the muscle cells to release CK so it is normal to detect some CK in the blood of healthy people. People with bigger muscles, such as fit young men, will naturally have a higher normal CK level than other people, such as older women. Some ethnic groups also have a naturally high CK level.
Many things can cause muscle damage and a higher than normal CK level. Heavy exercise can cause this, as well as muscle damage caused by a fall, a car accident, surgery or even an injection into a muscle. Some drugs, particularly cholesterol-lowering drugs (statins), can damage muscle and increase CK. If you are taking one of these drugs, let your doctor know if you experience any muscle pain or weakness. Some infections, such as influenza, can damage the muscles and cause a higher than normal CK level.
Other rarer causes of muscle damage causing a raised CK include muscle diseases that a person is born with and poor functioning of the thyroid gland (hypothyroidism).