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Serum or Plasma Creatinine Phosphokinase (CPK) Activity

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

This test measures the activity level of Creatine Phosphokinase (CPK), an enzyme found in heart, skeletal, and smooth muscle tissues. It helps assess muscle damage or heart-related conditions.

Quick summary

["CPK levels can indicate muscle or heart injury; higher levels may signal damage to these tissues."]

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

Key facts at a glance

LOINC
25229-6
Short code
PZA Islt Slgr Mcbct AB 100.0
Synonyms
PZA Islt Slgr Mcbct AB 100.0
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
method-for-slow-growing-mycobacteria-antibiotic-concentration-at-ug-ml
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 Creatine Phosphokinase (CPK)?

CPK, or Creatine Phosphokinase, is an enzyme that plays a role in energy production in cells. When muscle or heart tissue is damaged, CPK leaks into the bloodstream, raising its levels. This test helps doctors identify conditions like muscle injuries, heart attacks, or other muscle-related illnesses.

Why Might You Need This Test?

Your doctor may order a CPK test if you have symptoms like muscle weakness, pain, or unusual fatigue. It’s also used to monitor conditions like heart disease, muscle disorders, or after certain surgeries or injuries.

What to Expect Before the Test

No special preparation is needed for this test. You may have a small needle inserted into your arm or vein to draw blood. If you’re taking muscle relaxants or certain medications, let your doctor know.

What Are Normal Results?

There are no standard reference ranges provided here since they vary by lab and health status. Your doctor will compare your results to your baseline or expected values for your situation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK (Serum/Plasma)

Frequently asked questions

How high or low are my CPK levels?
If your CPK levels are significantly elevated, it may suggest muscle damage (e.g., from a workout, injury, or illness) or heart problems (e.g., a heart attack). If levels are very low, it could indicate muscle wasting or certain metabolic disorders. Always discuss results with your healthcare provider.
What causes CPK levels to rise?
CPK levels can rise due to muscle injury (e.g., from exercise, trauma, or overuse), heart attacks, stroke, or certain infections or toxins. Rarely, genetic disorders or muscle diseases may also affect CPK levels.
Can CPK levels be affected by diet or supplements?
Diet and supplements alone typically don’t change CPK levels, but some medications (e.g., statins, muscle relaxants) or supplements (e.g., creatine) may interact with test results. Always inform your doctor about all medications or supplements you take.
  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