Creatine Kinase MB Isoenzyme
Creatine kinase-MB (CK-MB) is a specific form of the CK enzyme found in relatively high amounts in heart muscle. A blood test measures how much of this heart-associated form is present.
Because CK-MB is concentrated in the heart, it has historically been used to help evaluate possible heart-muscle damage. Today it is often used alongside or in place of troponin depending on the setting. It is generally an acute, clinical-context test rather than a routine screen.
An elevated CK-MB can suggest injury to heart muscle, though skeletal muscle damage can also raise it. Because it is usually measured in acute situations, it is interpreted with symptoms, troponin, an ECG, and repeat testing. A single value should not be read on its own.
A low CK-MB is the expected normal finding and generally indicates no significant heart-muscle injury was detected. This is reassuring.
A low value within the normal range is typical for people without heart-muscle injury. Your clinician will interpret any result within your full clinical context.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.