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Serum Creatinine Phosphokinase (CPK) Activity

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

This test measures the activity of the enzyme Creatine Phosphokinase (CPK), which helps assess muscle, heart, or brain damage.

Quick summary

["CPK helps identify injuries to muscles, heart tissue, or nerves."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
40560-5
Short code
CK AE1/AE3 Ag Tiss Ql ImStn
Synonyms
CK AE1/AE3 Ag Tiss Ql ImStn
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
22
Ref high
198
Critical range
— – 10000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immune-stain
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 Is Creatine Phosphokinase (CPK) Used For?

CPK levels can indicate conditions like muscle injuries (e.g., from overexertion or trauma), heart attacks, or nerve disorders. High levels may suggest recent damage to these tissues.

How Is the Test Performed?

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

What Does a High or Low CPK Level Mean?

Elevated CPK levels often appear shortly after muscle injury, heart damage, or nerve issues. Very low levels may rarely indicate certain metabolic or genetic conditions.

Common Causes of Abnormal Results

High CPK levels can result from muscle strain, heart attacks, stroke, or conditions like myopathy. Low levels are less common but may relate to rare metabolic disorders.

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.

CPK is primarily used to monitor muscle, heart, or nerve damage. It’s often checked alongside other tests (e.g., troponin for heart damage) to diagnose conditions like myopathies, rhabdomyolysis, or neurological disorders.

Short name

CPK (Serum)

Frequently asked questions

Why might my doctor order this test?
Your doctor may order CPK testing if you have symptoms like muscle pain, weakness, or if they suspect conditions like a heart attack, stroke, or muscle injury.
How soon will I get my results?
Results are typically available within 24 to 48 hours, depending on your lab’s processing time.
Can I eat or drink before this test?
You can eat and drink normally before this test, as it does not require fasting.
  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