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Serum Creatinine Phosphokinase (CPK) Activity

Published: August 9, 2026Updated: August 17, 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 17, 2026Editorial policy

Key facts at a glance

LOINC
54158-1
Short code
Pan CK Ab Ser Ql IF
Synonyms
Pan CK Ab Ser Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
22
Ref high
198
Critical range
0.5 N/A – 10000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
CPT
82553
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 an enzyme found in heart, skeletal, and smooth muscle tissues. When these tissues are damaged—due to injury, illness, or conditions like a heart attack—the enzyme leaks into the bloodstream, raising its levels. This test helps doctors evaluate muscle or heart injury.

Why Might You Need This Test?

Your doctor may order CPK testing if you have symptoms like muscle pain, weakness, or chest discomfort, or if you’re suspected of having a heart attack, stroke, or other muscle disorders. It’s also used in monitoring conditions like myopathy or rhabdomyolysis.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where it’s processed to separate serum (the liquid part after clotting). The enzyme activity is then measured using a specialized lab technique.

Common Conditions Monitored

Elevated CPK levels can signal muscle damage from overexertion, infections, or metabolic disorders. High levels in the bloodstream may also indicate heart-related issues, such as a heart attack or myocarditis.

Reference range

Adult males: 22-198 U/L; Females: 22-198 U/LN/A

Specimen: serum

No special preparation required. Inform provider of any chest pain or symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK Serum

Frequently asked questions

When could my CPK levels be checked?
Your doctor may check CPK levels if you have unexplained muscle weakness, pain, or fatigue; if you’ve experienced chest pain or shortness of breath; or if you’re being evaluated for conditions like a heart attack, stroke, or muscle diseases.
What do my CPK results mean?
Elevated CPK levels suggest muscle or heart damage, but results alone don’t diagnose a specific condition. Your doctor will review your results alongside other tests, symptoms, and medical history to determine the next steps.
Can CPK levels be affected by diet or exercise?
Yes, physical activity or intense exercise can temporarily raise CPK levels, as muscle damage occurs during strenuous activity. However, chronic elevation may indicate an underlying muscle disorder that requires medical evaluation.
  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 17, 2026. · Read our editorial policy