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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 assess muscle damage or certain heart conditions.

Quick summary

["CPK helps identify muscle or heart tissue injury by detecting elevated enzyme levels in the blood."]

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

Key facts at a glance

LOINC
108285-8
Short code
M2-PK Ser-aCnc
Synonyms
M2-PK Ser-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 Is CPK Used For?

CPK is primarily used to evaluate muscle damage (myopathy) or heart-related issues, such as a heart attack. High levels may indicate recent trauma, exercise, or muscle disorders. In some cases, it can also signal heart problems like myocarditis or heart strain from conditions like heart failure.

How Is CPK Tested?

A small blood sample is drawn from your arm, and the enzyme activity is measured using a lab test. Results are typically reported in units per liter (U/L) or milliliters (mU/mL), though exact ranges vary by lab.

When Might You Need This Test?

Your doctor may order a CPK test if you have symptoms like muscle weakness, pain, or fatigue; if you’ve experienced a heart attack or other cardiac event; or if you’re suspected of having conditions like rhabdomyolysis (severe muscle breakdown) or certain neurological disorders.

What Are Common Causes of Elevated CPK?

High CPK levels can result from muscle injury (e.g., from exercise, trauma, or overuse), heart attacks, infections, or metabolic disorders. Certain medications or genetic conditions may also affect CPK levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK (Serum)

Frequently asked questions

Why do doctors check CPK levels?
Doctors check CPK levels to diagnose or monitor muscle or heart damage. For example, very high CPK can signal a heart attack or severe muscle injury, while moderate increases may indicate less severe conditions like exercise-induced muscle strain.
What should I do if my CPK test is abnormal?
If your CPK levels are elevated, your doctor may recommend further testing (like cardiac markers or imaging) to determine the cause. They may also adjust treatment, recommend rest, or suggest avoiding activities that strain your muscles.
Can CPK levels be affected by diet or supplements?
Yes, certain foods, vitamins, or supplements (like creatine or vitamin E) may influence CPK levels, but this effect is usually minor. Always discuss your diet and supplements with your doctor before testing.
  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