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Serum Creatinine Phosphokinase (CPK) Activity

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

This test measures the activity level of an enzyme called creatine phosphokinase (CPK), which helps assess muscle damage or certain heart conditions.

Quick summary

["CPK helps identify muscle or heart tissue injury by detecting elevated enzyme levels in the blood."]

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

Key facts at a glance

LOINC
39910-5
Short code
NM Hrt FP+WM+EF W RNC IV
Synonyms
NM Hrt FP+WM+EF 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

What Does CPK Measure?

CPK is found in heart, skeletal, and smooth muscle tissues. When these tissues are damaged—due to injury, illness, or overexertion—the enzyme leaks into the bloodstream, increasing its detectable levels in serum.

Why Might You Need This Test?

Doctors may order CPK testing to evaluate symptoms like muscle weakness, pain, or unexplained fatigue, or to monitor conditions such as heart attacks, muscle disorders, or certain infections.

Common Reasons for Testing

Common reasons include diagnosing conditions like myopathy (muscle disease), rhabdomyolysis (severe muscle breakdown), or assessing heart damage post-injury or during recovery from a cardiac event.

What to Expect Before the Test

No special preparation is needed, but inform your healthcare provider about recent muscle injuries, medications (especially steroids), or conditions like dehydration or kidney disease.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK (Serum)

Frequently asked questions

Elevated CPK levels may indicate muscle damage, but they can also be influenced by factors like age, exercise, or certain medications. High levels can signal underlying conditions requiring further medical evaluation.
How long does it typically take to get results?
Results are usually available within 24 to 48 hours, depending on lab processing times. Your doctor will discuss findings during your follow-up visit.
Can CPK levels be affected by diet or exercise?
Yes, intense physical activity or muscle strain can temporarily raise CPK levels. However, chronic elevation may warrant further investigation for conditions like muscle disorders or heart disease.
High levels may prompt additional testing (e.g., muscle biopsy, imaging) to rule out serious conditions. Low levels are less concerning but could be noted if monitoring a known muscle disorder or heart condition.
  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