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Serum Creatinine Phosphokinase (CPK) Activity

Published: August 9, 2026Updated: August 16, 2026

This test measures the activity of an enzyme called creatine phosphokinase (CPK), which helps your body produce energy from muscles and other tissues. CPK levels can rise if muscle tissue is damaged.

Quick summary

["CPK helps doctors assess muscle injury or certain heart conditions."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
18574-4
Short code
J Pnt ST Amp+80ms L-V1
Synonyms
J Pnt ST Amp+80ms L-V1
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ekg
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

What Does CPK Measure?

CPK is an enzyme found in heart muscle, skeletal muscle, and the brain. When muscles are injured—such as from exercise, trauma, or conditions like myositis—the enzyme leaks into the bloodstream, increasing its levels. Elevated CPK can also signal heart damage, such as from a heart attack.

Why Might You Need This Test?

Your doctor may order CPK testing if you have symptoms like muscle pain, weakness, or unexplained fatigue. It’s also used to monitor conditions like muscle disorders, heart attacks, or other injuries requiring muscle tissue assessment.

Common Causes of Elevated CPK Levels

High CPK levels may occur due to muscle strain (e.g., intense exercise), muscle diseases (e.g., muscular dystrophy), or conditions like rhabdomyolysis (severe muscle breakdown). In rare cases, it can signal heart or neurological issues.

What to Expect Before or After the Test

No special preparation is needed. A blood sample is taken from a vein, usually in your arm. Results may take a few days to arrive, depending on your lab.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Elevated CPK Levels

Short name

CPK (Serum)

Frequently asked questions

How Long Does It Take to Get Results?
Results are typically available within 24 to 72 hours, but timing varies by lab. Follow-up with your doctor if you have concerns about your results.
Can CPK Levels Be Low?
Low CPK levels are less common but may occur in certain genetic conditions or if muscle tissue is severely depleted. Your doctor will discuss results in context with your health history.
Does CPK Test Differentiate Between Muscle vs. Heart Damage?
No, CPK alone doesn’t distinguish between muscle or heart injury. Your doctor may order additional tests (e.g., cardiac enzymes) if heart involvement is suspected.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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 16, 2026. · Read our editorial policy