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Serum Creatinine Phosphokinase (CPK) or Creatine Kinase (CK) Activity

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

This test measures the activity of creatine kinase, an enzyme that helps convert creatine to phosphocreatine, which supplies energy to cells. It helps assess muscle damage or injury.

Quick summary

["This test helps identify muscle-related issues or conditions affecting energy production in cells."]

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

Key facts at a glance

LOINC
39923-8
Short code
NM Hrt Gated+EF Rest+W RNC IV
Synonyms
NM Hrt Gated+EF Rest+W RNC IV
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
nm
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 Is This Test Done?

Your healthcare provider may order this test to check for muscle damage, such as from overexertion, injury, or certain medical conditions. It can also help diagnose or monitor conditions like heart attacks, myopathies (muscle diseases), or other muscle-related disorders.

Common Causes of Elevated or Low Results

High levels of CPK/CK may indicate recent muscle injury, overexertion, or conditions like myocarditis (heart muscle inflammation), stroke, or certain medications. Low levels are less common and may rarely suggest muscle wasting or severe muscle disease.

How Is This Test Performed?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where the enzyme activity is measured using specialized equipment.

What Does the Test Result Mean?

Results are compared to a reference range for your age and sex. Elevated levels often signal muscle damage or other underlying issues, while low levels may require further evaluation to rule out rare conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Elevated CPK/CK levels can signal acute muscle injury, cardiac events, or metabolic disorders. Monitoring these levels helps guide treatment decisions for conditions like rhabdomyolysis (severe muscle breakdown) or neuromuscular diseases.

Short name

CPK/CK Activity

Frequently asked questions

What are the typical reference ranges for CPK/CK?
Reference ranges vary by lab and individual factors like age, sex, and health status. Your specific range will be provided with your results.
How long does it take to get my CPK/CK test results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time.
Can I take anything by mouth before this test?
You may eat and drink normally unless instructed otherwise by your healthcare provider. Avoiding strenuous exercise or heavy lifting before the test can help ensure accurate results.
  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