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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, heart, or brain damage.

Quick summary

["CPK helps identify injuries to muscles, heart tissue, or nerves."]

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

Key facts at a glance

LOINC
68377-1
Short code
ENA RNP 63kD Ab SerPl Ql
Synonyms
ENA RNP 63kD Ab SerPl 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 muscles, and brain cells. When these tissues are damaged—due to injury, illness, or stress—the enzyme leaks into the bloodstream. Measuring CPK helps doctors determine if you have muscle tears, heart problems (like a heart attack), or nerve disorders.

Why Might You Need This Test?

Your doctor may order CPK if you have symptoms like muscle pain, weakness, chest pain, or unexplained fatigue. It’s also used to monitor conditions like myopathy (muscle disease), heart attacks, or nerve injuries.

Common Reasons for Testing

Common reasons include diagnosing muscle injuries, checking for heart damage after a suspected attack, or evaluating nerve-related conditions. It’s sometimes used alongside other tests to confirm or guide treatment.

What to Expect Before the Test

No special preparation is needed, but avoid strenuous exercise 24 hours before testing to get the most accurate results. Tell your doctor about any medications or recent injuries.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK Serum

Frequently asked questions

Why did my doctor order this test?
Your doctor may have noticed symptoms like muscle pain, weakness, or heart-related concerns. CPK helps identify whether tissue damage is occurring in your muscles, heart, or nerves.
What do my CPK results mean?
Results alone don’t diagnose a condition—they’re part of a bigger picture. Your doctor will compare your levels to your symptoms and other tests to determine next steps.
Can I lower my CPK levels naturally?
While you can’t change CPK levels directly, managing conditions like diabetes, high blood pressure, or muscle overuse may help. Avoid excessive exercise or trauma to affected areas, and follow your doctor’s advice.
  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