CK-MB (Creatine Kinase MB)

What is CK-MB?

CK-MB is one of the three subtypes of the enzyme creatine kinase. While most creatine kinase is found in skeletal muscles as CK-MM, CK-MB is found in the highest proportion in heart muscle. In healthy people, the amount of CK-MB in the blood is very low. When heart muscle cells are damaged, CK-MB passes into the blood and its amount in the blood starts to rise within a few hours.

This test measures the amount of CK-MB in the blood as mass, and the result is reported in ng/mL. The measurement is performed with antibody-based immunoassay methods and is more sensitive than older methods based on enzyme activity. Because CK-MB is also present in small amounts in skeletal muscles, it can also rise with serious muscle injuries; for this reason, the result is often interpreted together with total CK.

When is the CK-MB test ordered?

CK-MB was widely used in the past to diagnose heart attacks, but today it has largely been replaced by troponin tests. Even so, your doctor may order CK-MB to evaluate damage to the heart muscle, to estimate when it occurred, or in situations where troponin is difficult to interpret.

Because CK-MB is cleared from the blood faster than troponin, it can provide additional information for detecting new damage that occurs a few days after a heart attack. When total CK is high, it also helps distinguish whether the increase comes from the heart muscle or from the skeletal muscles. It may also be measured for follow-up after heart surgery and procedures on the heart's blood vessels.

• Evaluation together with troponin when heart muscle damage is suspected
• Monitoring for new damage after a heart attack
• Follow-up after heart surgery or interventional procedures
• Suspected inflammation of the heart muscle (myocarditis)
• Investigating the source of elevated total CK

How should you prepare for the CK-MB test?

No fasting is required for CK-MB, and the sample can be taken at any time of day. Because strenuous exercise and muscle injuries can affect CK-MB as well as total CK, it is recommended that you avoid intense physical activity for a day or two before the test. If you take high-dose biotin, also known as vitamin B7, as a supplement, tell your doctor; this vitamin can lead to misleading results in some antibody-based measurements.

If you have symptoms such as chest pain, shortness of breath, cold sweats or pain spreading to the arm and jaw, do not wait for a test appointment; call 112 immediately. For planned check-up tests, the blood sample is taken from the arm, and our nurse can do this at your home or workplace. Unless your doctor tells you otherwise, keep taking your heart medicines as usual.

What does the CK-MB result mean?

High CK-MB suggests that there may be damage to the heart muscle; elevations can be seen after a heart attack, inflammation of the heart muscle, heart surgery or procedures on the heart. However, non-cardiac causes such as severe skeletal muscle injuries, certain muscle diseases and kidney failure can also increase the value. Mild elevations may also be seen after very intense endurance sports such as a marathon. For this reason, a single CK-MB result is not sufficient to diagnose a heart attack.

After damage to the heart muscle, CK-MB rises within a few hours and usually returns to normal within two to three days; this is why your doctor sometimes orders serial measurements. A normal result does not by itself rule out a heart problem, especially if the symptoms started very recently or passed several days ago. Reference ranges differ by laboratory, method and sex, and age may also have an effect; this page shows the range of the relevant laboratory. Your result must always be interpreted by a doctor, together with your symptoms and other tests such as an ECG and troponin.