Serum Creatinine Kinase (CK) Isoenzyme MB Fraction
This test measures the fraction of Creatinine Kinase (CK) that comes from heart muscle, called the CK-MB isoenzyme. It helps assess heart muscle damage or injury.
["This test helps doctors check for heart problems after injury, heart attack, or other conditions that may affect heart muscle."]
Key facts at a glance
- LOINC
- 9643-8
- Short code
- CK MM CFr SerPl
- Synonyms
- CK MM CFr SerPl
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 22
- Ref high
- 198
- Critical range
- — – 10000 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82553
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Your doctor may order this test if you’ve experienced symptoms like chest pain, shortness of breath, or unusual fatigue, especially after a suspected heart attack, injury, or surgery. It can also be used to monitor heart health in people with known heart conditions or after a heart procedure.
What to Expect Before the Test
No special preparation is needed. You’ll typically provide a blood sample drawn from a vein in your arm. If you’re on blood-thinning medication or have a history of bleeding disorders, let your doctor know before the test.
What the Test Results Mean
Elevated levels of CK-MB can indicate heart muscle damage, but results alone aren’t diagnostic. They’re usually interpreted alongside other tests, symptoms, and medical history. Your doctor will discuss the meaning of your specific results with you.
Common Reasons for Testing
This test is often used to diagnose or evaluate conditions such as a heart attack (myocardial infarction), heart muscle inflammation (myocarditis), or other heart-related issues. It may also help determine the extent of damage after a heart procedure or injury.
Reference range
Adult males: 22-198 U/L; Females: 22-198 U/LN/A
No special preparation required. Inform provider of any chest pain or symptoms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
CK-MB is a specific form of the enzyme CK that primarily comes from heart tissue. When heart muscle is damaged, CK-MB levels rise in the blood within hours. This makes it useful for identifying recent heart injury, guiding treatment decisions, or monitoring recovery. However, false elevations can occur with muscle injuries or certain medications, so results should be interpreted carefully in the context of your overall health.
Short name
CK-MB Fraction
Frequently asked questions
What does an elevated CK-MB level mean?
Can stress or exercise cause a false positive?
How long does it take for CK-MB levels to return to normal?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy