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Serum or Plasma Creatinine Phosphokinase (CPK) Activity

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

This test measures the activity of an enzyme called creatine phosphokinase, which helps produce energy in your muscles. Elevated levels may indicate muscle damage or certain conditions.

Quick summary

["CPK helps assess muscle health and identify potential injuries or disorders affecting your muscles."]

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

Key facts at a glance

LOINC
7688-5
Short code
Sardine IgG Qn
Synonyms
Sardine IgG Qn
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
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 muscle cells are damaged—due to injury, exercise, or illness—the enzyme leaks into the bloodstream. This test quantifies the amount of CPK present in your serum or plasma.

Why Is CPK Tested?

Doctors may order a CPK test to diagnose or monitor conditions such as muscle injuries (e.g., strains, tears), heart attacks, or certain neurological disorders. It can also help evaluate symptoms like muscle weakness, pain, or fatigue.

When Might You Need This Test?

You might receive a CPK test if you experience unexplained muscle pain, weakness, or cramping, especially after physical activity. It may also be part of a broader evaluation for conditions like myopathies (muscle diseases) or heart-related issues.

What to Expect Before the Test

No special preparation is usually needed, but avoid intense exercise 24 hours before testing if possible. If you’re taking medications that affect muscle function, inform your healthcare provider.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK (Creatine Phosphokinase)

Frequently asked questions

What are normal CPK levels?
Normal CPK levels vary by lab and individual, but reference ranges typically fall between 24–200 units per liter (U/L) for adults. These ranges can differ based on sex, age, and health status.
Will CPK levels always be high if I have muscle damage?
Not necessarily. CPK levels may rise only after significant muscle damage or prolonged exertion. Some people with muscle disorders may have consistently elevated levels, while others may not show changes until severe damage occurs.
Can CPK test results affect my medication?
Yes, if your CPK levels are very high, your doctor may adjust medications that affect muscle function, such as statins or certain antibiotics, to prevent further harm to your muscles.
  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