Serum or Plasma Creatinine Phosphokinase (CPK) or Lactate Dehydrogenase (LDH) Activity
This test measures the activity of enzymes (CPK or LDH) found in your blood. These enzymes help break down energy in cells and can rise if your muscles, heart, or other tissues are damaged.
["Enzymes in your blood can signal tissue injury or stress."]
Key facts at a glance
- LOINC
- 1356-5
- Short code
- 11DC 8h p 30 mg/kg MTP PO SerPl-mCnc
- Synonyms
- 11DC 8h p 30 mg/kg MTP PO SerPl-mCnc
- Category
- hormone
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 8
- Ref high
- 61
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82977
- 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
Why This Test Is Done
Your doctor may order this test to check for conditions that damage muscles, heart tissue, or other organs. For example, it can help identify muscle injuries, heart attacks, or certain infections.
What to Expect Before the Test
No special preparation is needed. You may have a small needle inserted into a vein in your arm to draw blood. If you’re taking medications that affect muscle function, let your doctor know.
What the Results Mean
Higher-than-normal levels may suggest recent tissue damage, but results alone don’t confirm a diagnosis. Your doctor will review them with your full medical history and other test results.
Common Conditions Linked to Elevated Levels
Elevated CPK or LDH can be linked to muscle injuries (e.g., from exercise or trauma), heart attacks, liver disease, or infections like the flu. Low levels may raise concerns about severe muscle wasting or certain blood disorders.
Reference range
Adult males: 8-61 U/L; Adult females: 5-36 U/LN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test helps doctors monitor conditions like muscle disorders, heart disease, or metabolic disorders by tracking enzyme activity over time. It’s often used alongside other tests for a complete picture.
Short name
CPK/LDH Activity
Frequently asked questions
What causes CPK or LDH levels to rise?
How soon after injury or illness might results change?
Can diet or exercise affect these test results?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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