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Serum Creatinine Phosphokinase (CPK) Activity

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

This test measures the activity of creatine phosphokinase (CPK), an enzyme found in heart, muscle, and brain tissues. It helps assess damage to these organs.

Quick summary

["CPK levels can indicate muscle, heart, or brain injury."]

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

Key facts at a glance

LOINC
111376-0
Short code
Hu Ab Msmt Ser
Synonyms
Hu 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 This Test Measure?

Creatine phosphokinase (CPK), also called creatine kinase (CK), is an enzyme that helps produce energy in cells. When tissues like the heart, muscles, or brain are damaged, CPK leaks into the bloodstream. This test measures how much CPK is present in your serum, reflecting recent injury or stress to these areas.

Why Might This Test Be Ordered?

Your healthcare provider may order this test to diagnose or monitor conditions such as heart attacks, muscle injuries (e.g., from overexertion or trauma), or neurological issues. It can also help evaluate symptoms like chest pain, muscle weakness, or unexplained fatigue.

Common Reasons for Testing

Common reasons include evaluating symptoms of a heart attack (e.g., chest pain, shortness of breath), assessing muscle disorders (e.g., myositis, rhabdomyolysis), or investigating unexplained neurological symptoms (e.g., weakness, confusion).

What to Expect Before the Test

No special preparation is needed, but avoid intense exercise or strenuous activity 24 hours before testing, as it may raise CPK levels temporarily.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK Serum

Frequently asked questions

How long does it take for CPK levels to rise after injury?
CPK levels can rise within hours after muscle or heart damage. For example, heart attack CPK peaks around 18–24 hours post-event. Muscle injury may show elevated levels within 6–12 hours. Always follow up with your provider for interpretation.
Can CPK levels be affected by medications?
Some medications, like certain steroids or some antibiotics, may influence CPK levels. If you’re on medication, discuss it with your provider before testing.
Is CPK testing painful or uncomfortable?
No, this test involves a simple blood draw, similar to other routine blood tests. You may feel a slight pinch, but it’s brief and usually well-tolerated.
  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