Lactate Dehydrogenase (LDH) Activity in Serum/Plasma
This test measures the activity level of the enzyme lactate dehydrogenase (LDH) in your blood. LDH helps convert lactate to pyruvate and is found in many tissues, including the heart, liver, and muscles.
["LDH helps your body convert lactate into energy and can be elevated in certain health conditions."]
Key facts at a glance
- LOINC
- 51515-5
- Short code
- LDH3 CFr Prt Elph
- Synonyms
- LDH3 CFr Prt 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
What Does LDH Measure?
LDH is an enzyme that plays a role in energy production. It helps convert lactic acid into pyruvate, which can then enter the body’s energy cycle. Elevated LDH levels may suggest damage to cells in organs like the heart, liver, kidneys, or muscles, as well as certain blood disorders or infections.
Why Is LDH Tested?
Doctors may order an LDH test to investigate symptoms such as chest pain, unexplained fatigue, muscle weakness, or signs of organ damage. It can also be part of a broader evaluation for conditions like heart attacks, liver disease, anemia, or infections.
Common Causes of Elevated LDH Levels
High LDH levels can result from conditions like heart attacks, liver disease, kidney problems, certain cancers, blood disorders (such as hemolytic anemia), or infections. Low LDH levels are less common but may occur in rare metabolic or genetic disorders.
How Is the Test Performed?
A blood sample is taken from a vein in your arm. The sample is sent to a lab where LDH activity is measured using an enzymatic method. No special preparation is usually needed, but you may be asked to avoid strenuous activity or certain medications before testing.
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.
Elevated LDH levels often indicate tissue damage or disease processes, but they can also be influenced by factors like age, exercise, or certain medications. LDH is sometimes used alongside other tests to help diagnose conditions like myocardial infarction (heart attack), liver disease, or muscle disorders. However, it is not always definitive on its own.
Short name
LDH Activity
Frequently asked questions
When might I need to take this test?
What do my LDH results mean?
Can lifestyle or diet affect LDH levels?
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