Lactate Dehydrogenase (LDH) Isoenzyme Activity (Serum/Plasma)
This test measures different forms (isoenzymes) of the enzyme lactate dehydrogenase (LDH) in your blood. It helps identify which specific isoenzyme is elevated, which can indicate where in your body damage or disease may be occurring.
["Elevated isoenzyme patterns may signal tissue injury in organs like the heart, liver, or muscles."]
Key facts at a glance
- LOINC
- 2545-2
- Short code
- LDH4 CFr SerPl Elph
- Synonyms
- LDH4 CFr SerPl Elph
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 140
- Ref high
- 280
- Critical range
- 7.2 N/A – 7.6 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- electrophoresis
- CPT
- 83615
- 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 Might Be Ordered
Your healthcare provider may order this test to investigate symptoms such as chest pain, unexplained fatigue, or signs of organ damage. It can also be used to monitor conditions like heart attacks, liver disease, or muscle disorders. LDH isoenzyme patterns help pinpoint which tissue is affected.
How the Test Works
LDH is an enzyme found in many cells, including those in the heart, liver, kidneys, muscles, and red blood cells. The test measures different LDH isoenzymes using electrophoresis, a method that separates these forms based on their electrical charge. This helps determine which tissues may be damaged.
Common Reasons for Testing
A provider might order this test if you have symptoms like persistent chest pain, jaundice (yellowing of skin/eyes), muscle weakness, or unexplained fatigue. It can also be used to diagnose or monitor conditions such as myocardial infarction (heart attack), liver disease, or certain cancers.
What to Expect Before the Test
No special preparation is needed for this test. You may have a blood sample drawn from a vein in your arm. If you’re on blood-thinning medication, let your provider know before the test.
Reference range
Adult: 140-280 U/LN/A
No special preparation required. Inform provider of any chest pain or symptoms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
LDH Isoenzyme Profile
Frequently asked questions
What Does an Elevated LDH Isoenzyme Mean?
How Does This Test Differ from a General LDH Test?
Can This Test Be Used to Diagnose a Specific Condition?
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