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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 damage or certain heart conditions.

Quick summary

["CPK levels can signal muscle or heart injury and guide treatment decisions."]

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

Key facts at a glance

LOINC
110678-0
Short code
RA Nuc Ab Msmt Ser
Synonyms
RA Nuc 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, is an enzyme found primarily in heart, skeletal, and brain tissues. When muscle or heart tissue is damaged, CPK leaks into the bloodstream, increasing its levels. This test quantifies the amount of CPK activity in your serum to identify potential damage.

Why Might You Need This Test?

Doctors may order a CPK test to diagnose or monitor conditions like heart attacks, muscle injuries (such as from overexertion or trauma), or certain neurological disorders. It can also help evaluate symptoms like chest pain, muscle weakness, or unexplained fatigue.

Preparation and Sample Collection

No special preparation is needed for this test. A blood sample is drawn from a vein, usually in your arm, by a healthcare professional. The sample is sent to a lab for analysis.

What Are Possible Results?

Results are reported in units per liter (U/L) or milliliters (mU/mL), depending on the lab’s method. Elevated CPK levels may indicate muscle or heart damage, while normal levels suggest healthy tissue function. Interpretation depends on clinical context and other test results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK Serum

Frequently asked questions

What Are Common Causes of Elevated CPK Levels?
Elevated CPK levels can result from muscle injuries (e.g., from exercise, trauma, or overuse), heart attacks, stroke, or certain neurological conditions. Chronic conditions like myopathies (muscle diseases) or metabolic disorders may also affect CPK levels. Always discuss your results with your healthcare provider.
What Are Common Causes of Low CPK Levels?
Low CPK levels are less common but may occur in conditions like severe muscle wasting, certain genetic disorders, or during recovery from muscle damage. Rarely, medications or lab errors can cause false-low results. Your doctor will consider your medical history and other tests.
How Often Should This Test Be Done?
The frequency of this test depends on your health condition and treatment plan. If you have a known muscle or heart condition, your doctor may recommend regular monitoring. Follow-up tests are often scheduled based on symptoms or clinical needs.
  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