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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 levels can signal injury to organs that use a lot of energy, like the heart or muscles."]

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

Key facts at a glance

LOINC
6394-1
Short code
ECV40 Ab Titr Ser CF
Synonyms
ECV40 Ab Titr Ser CF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
comp-fix
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 high amounts in heart, skeletal, and brain tissues. When these tissues are damaged (e.g., from a heart attack, muscle injury, or stroke), CPK leaks into the bloodstream. This test helps doctors detect early signs of injury to these organs.

Why Might You Need This Test?

Your doctor may order CPK testing if you have symptoms like chest pain, muscle weakness, confusion, or after a suspected heart attack, stroke, or severe muscle injury. It can also help monitor conditions like heart disease or muscle disorders.

How Is the Test Done?

A blood sample is taken from a vein in your arm. The sample is sent to a lab, where CPK activity is measured using an enzymatic method.

What Are Common Results?

Results are reported as CPK activity levels (units per liter), but exact reference ranges can vary by lab. High levels may indicate tissue damage, while very low levels could suggest muscle wasting or certain metabolic disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: CPK Levels and Health

Short name

CPK (Serum)

Frequently asked questions

Why might my CPK levels be checked during a heart attack?
During a heart attack, CPK levels rise within hours as damaged heart muscle releases the enzyme into your blood. Early detection helps doctors start treatment quickly.
What if my CPK levels are elevated?
Elevated CPK can signal muscle damage (e.g., from exercise, injury, or conditions like myositis), heart issues, or neurological problems. Your doctor will discuss symptoms and other tests to determine the cause.
Could my CPK levels be affected by medications?
Some medications (e.g., statins, some antibiotics) may lower CPK levels, while others (like certain muscle relaxants) could raise them. Always ask your doctor about how your medications might influence test results.
  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