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Creatine Kinase-MB (Activity) Unit Converter
Creatine Kinase-MB (CK-MB) Activity measures the enzymatic rate of the MB isoenzyme of Creatine Kinase. This isoenzyme is found predominantly in the myocardium (heart muscle). Historically, the activity assay was the primary method for diagnosing myocardial infarction (heart attack) but has largely been replaced by more sensitive and specific assays, such as CK-MB **mass** and Troponin.
The activity assay is less specific than the modern mass assay and can be affected by interference from macro-CK. Nevertheless, it tracks the timeline of cardiac injury, rising 3–12 hours after the onset of chest pain, peaking at 24 hours, and returning to normal within 48–72 hours. Results are reported in enzyme activity units, with the SI standard being the **katal** ($\mu\text{kat/L}$).
SI Units
RecommendedMicrokatals and Nanokatals per liter.
Conventional Units
Clinical Context
Reference Range: Normal CK-MB activity is typically low, generally < 25 U/L, though this varies significantly by assay method and temperature.
The CK-MB Relative Index is necessary to confirm cardiac damage when total CK is elevated (e.g., in skeletal muscle injury). For true cardiac injury, the ratio of CK-MB activity to total CK activity must be high (though the newer mass assay is preferred). The conversion factor is constant: 1 U/L $\approx$ 0.0167 µkat/L.
Clinical References
How to Use This Calculator
Follow these steps to get accurate clinical conversions instantly.
Enter Values
Input your laboratory results into the corresponding unit field (e.g., U/L). You can use either dot or comma decimals.
Automatic Conversion
The calculator works in real-time. As you type in one field, all other units (like µkat/L or kU/L) are instantly updated.
Verify Units
Check the SI Units section. µkat/L is the standard ISO unit for enzyme activity.
Reset
Use the Clear button to reset all fields before starting a new calculation.
Frequently Asked Questions & Tips
CK-MB is an enzyme. Clinical labs measure its catalytic activity (rate of reaction), not its mass.
Yes, U/L and IU/L (International Units per Liter) are interchangeable.