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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 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
30766-0
Short code
XR Pelvis 3V
Synonyms
XR Pelvis 3V
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
xr
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 CPK Used For?

CPK levels are often checked after injuries like muscle strains, heart attacks, or other conditions that may damage muscle or heart cells. High CPK can signal recent trauma, exercise-induced muscle damage, or conditions affecting the heart or nerves.

Why Might My CPK Test Be Ordered?

Your doctor may order this test if you’ve experienced unexplained muscle weakness, chest pain, or symptoms like nausea, shortness of breath, or fatigue. It may also be used to monitor conditions like myocarditis (heart inflammation), nerve disorders, or muscle diseases.

What Does a High or Low CPK Level Mean?

Elevated CPK levels may indicate recent muscle injury, heart damage, or conditions like myositis (muscle inflammation). Very low levels could suggest muscle wasting, severe malnutrition, or rare metabolic disorders.

How Is CPK Tested?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where CPK activity is measured using an automated enzyme assay.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CPK plays a key role in diagnosing muscle or heart damage by detecting enzyme leakage into the bloodstream after tissue injury. It’s particularly useful for identifying conditions like myocardial infarction (heart attack), rhabdomyolysis (severe muscle breakdown), or neuromuscular disorders.

Short name

CPK Serum

Frequently asked questions

Why did my doctor request this test?
Your doctor may have noticed symptoms like muscle pain, weakness, or heart-related concerns. CPK helps rule out muscle damage, heart issues, or other conditions affecting these organs.
What are the normal results?
Normal results vary by lab and age, but elevated levels often signal recent injury or disease. Your doctor will interpret results in relation to your symptoms and overall health.
Can I do anything to lower my CPK levels?
If elevated due to muscle strain, rest and gentle exercise may help. For heart-related causes, follow your doctor’s advice on lifestyle changes or medications.
  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