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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 levels can signal muscle or heart tissue injury."]

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

Key facts at a glance

LOINC
23270-2
Short code
M cap caprip Ag Tiss Ql
Synonyms
M cap caprip Ag Tiss Ql
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 Does CPK Measure?

CPK is an enzyme found in heart, skeletal, and smooth muscle cells. When these muscles are damaged—due to injury, illness, or conditions like a heart attack—the enzyme leaks into the bloodstream. This test quantifies how much CPK is present, helping doctors identify areas of tissue stress or injury.

Why Might You Need This Test?

Your doctor may order a CPK test if you have symptoms like muscle pain, weakness, or unexplained fatigue. It’s also used to monitor conditions affecting muscle or heart function, such as myopathies, myocarditis, or after procedures like heart surgery.

Common Causes of Elevated CPK Levels

High CPK levels can result from muscle injuries (e.g., strains, cramps), certain infections, or metabolic disorders. In the heart, elevated CPK may signal early signs of a heart attack or other cardiac stress.

What Does a Low CPK Level Mean?

Low CPK levels are less common but may occur in conditions like severe muscle wasting, certain genetic disorders, or during extreme dehydration. Your doctor will consider your overall health and symptoms when interpreting results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK Serum

Frequently asked questions

How is CPK Tested?
This test involves drawing blood from a vein in your arm. The sample is sent to a lab where the CPK enzyme activity is measured using an immunoassay or enzymatic method. Results are typically available within 24–48 hours.
How Often Should You Get This Test?
The frequency depends on your medical condition. For example, people with muscle disorders may need regular monitoring, while others may only get it once for diagnostic purposes.
What Are the Risks of This Test?
The most common risk is mild discomfort or bruising at the needle insertion site. Rarely, there may be a slight reaction to the blood draw, such as swelling or redness.
  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