Skip to content

Serum Creatinine Phosphokinase (CPK) Activity

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

This test measures the activity of the enzyme creatine phosphokinase (CPK), which helps assess muscle damage or injury.

Quick summary

["CPK helps identify muscle-related issues or damage."]

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

Key facts at a glance

LOINC
110855-4
Short code
EIV A2 Ab Msmt Ser
Synonyms
EIV A2 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 Is Creatine Phosphokinase (CPK)?

Creatine phosphokinase (CPK), also called creatine kinase (CK), is an enzyme found mostly in heart, skeletal, and smooth muscle cells. When muscle tissue is damaged—due to injury, exercise, or conditions like myositis—the enzyme leaks into the bloodstream. This test measures the amount of CPK in your serum to help detect muscle injury or related problems.

Why Might You Need This Test?

Your doctor may order a CPK test if you have symptoms like muscle weakness, pain, or tenderness, or if you’ve experienced recent trauma, exercise, or conditions that could damage muscle tissue. It’s also used to monitor certain heart conditions or to check for complications from medications that affect muscles.

Common Causes of Elevated CPK Levels

High CPK levels can result from muscle damage caused by exercise, injuries, infections, or conditions like myopathy (muscle disease). In rare cases, it may also be linked to heart problems, seizures, or certain medications.

What Does a Low CPK Level Mean?

Low CPK levels are less common and may indicate muscle atrophy, certain genetic disorders, or conditions that suppress muscle activity. Your doctor will consider your overall health and symptoms when interpreting results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance of CPK Levels

Short name

CPK Serum

Frequently asked questions

Could my CPK test results affect my treatment plan?
Yes, elevated CPK levels may prompt further evaluation for muscle-related issues, such as imaging tests or additional blood work. Your doctor will discuss findings with you and adjust treatment if needed, such as modifying medications or managing symptoms.
Is CPK testing always done with other blood tests?
Sometimes, CPK is ordered alone, but it’s often included in panels for muscle or heart conditions. Your doctor may also check other markers like troponin (heart damage) or aldolase (muscle breakdown) if symptoms suggest a specific concern.
How soon will I get my CPK test results?
Results are typically available within 1–3 business days, depending on your lab. Your doctor will contact you with the final report and any follow-up steps.
  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