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Serum or Plasma Creatinine Phosphokinase (CPK) Activity

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

This test measures the activity of an enzyme called creatine phosphokinase, which helps break down energy in your muscles. High levels may indicate muscle damage or injury.

Quick summary

["CPK helps assess muscle health and identify potential damage from exercise, injury, or certain medical conditions."]

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

Key facts at a glance

LOINC
109376-4
Short code
EBV EA-R Ab Msmt Ser
Synonyms
EBV EA-R Ab Msmt Ser
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 tissues. When muscle cells are damaged, CPK leaks into the bloodstream, raising its levels. This test helps doctors evaluate muscle injury, heart problems, or other conditions affecting muscle function.

Why Is CPK Tested?

Doctors may order a CPK test to diagnose or monitor conditions such as muscle disorders, heart attacks, or complications from certain medications or treatments. It’s also used to check for muscle weakness or pain that may signal underlying issues.

Common Causes of Elevated CPK Levels

High CPK levels can result from muscle strain (e.g., overexertion, cramps), injuries (e.g., bruises, fractures), or conditions like myositis (inflammation of muscles). Heart attacks, certain infections, or metabolic disorders may also raise CPK.

When Might CPK Levels Be Low?

Low CPK levels are less common but may occur in rare genetic muscle disorders or severe muscle wasting. Chronic illnesses or certain medications could also affect enzyme activity.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK (Creatine Phosphokinase)

Frequently asked questions

What Does It Mean If My CPK Test Is Abnormal?
If your CPK is elevated, your doctor may recommend further testing (e.g., imaging, additional bloodwork) to determine the cause. If low, it may warrant investigation into muscle disorders or other underlying health concerns.
How Is CPK Tested?
A blood sample is drawn, and the enzyme activity is measured using an automated lab test. Results are compared to reference ranges for your age and sex.
What Are Typical CPK Reference Ranges?
Reference ranges vary by lab and individual factors (e.g., age, sex). Your doctor will interpret results in the context of your overall health and symptoms.
  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