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Serum 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, muscle, and brain tissues. It helps assess damage to these organs, often due to injury, illness, or other conditions.

Quick summary

["CPK levels can signal muscle or heart damage; high results may indicate injury or disease."]

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

Key facts at a glance

LOINC
34709-6
Short code
C trach Ag Nph Ql
Synonyms
C trach Ag Nph Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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)?

Creatine Phosphokinase (CPK), also called Creatine Kinase (CK), is an enzyme that plays a key role in energy production in cells. It exists in three main forms—CPK-MB (heart muscle), CPK-MM (skeletal muscle), and CPK-BB (brain). This test specifically measures CPK levels in your blood, which can rise when tissues are damaged or stressed.

Why Might You Need This Test?

Doctors may order a CPK test to investigate symptoms like chest pain, muscle weakness, or unexplained fatigue. It can also help diagnose conditions such as heart attacks, muscle injuries, or neurological disorders.

When Are CPK Levels Elevated?

High CPK levels often appear shortly after muscle or heart damage, such as from a heart attack, severe muscle injury (e.g., from a car accident or intense exercise), or conditions like myositis or stroke. However, CPK can also rise gradually with chronic muscle overuse or certain metabolic disorders.

What Could Low CPK Levels Indicate?

Low CPK levels may suggest muscle atrophy, certain genetic disorders, or conditions affecting energy metabolism. They are less common but can occur in some cases of malnutrition or severe illness.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

CPK (Serum)

Frequently asked questions

How Is This Test Done?
A blood sample is taken from a vein in your arm. The lab then measures CPK activity using an immunoassay or enzymatic method to determine your level.
What Do My Results Mean?
Your doctor will compare your CPK result to a reference range (which varies by lab) and consider your symptoms, medical history, and other test results. Very high levels may require further evaluation, while low levels may prompt additional investigation for underlying causes.
What Are Common Causes of Low CPK?
Low CPK levels are less common but may result from muscle wasting, malnutrition, or certain genetic disorders. Chronic illness or medications that affect muscle function could also play a role.
  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