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Lactate Dehydrogenase (LDH) Activity in Serum/Plasma

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

This test measures the activity of the enzyme lactate dehydrogenase (LDH), which plays a role in converting lactate to pyruvate during energy production in cells. It helps assess tissue damage, metabolic health, and certain conditions.

Quick summary

["LDH helps identify potential tissue injury or metabolic issues by measuring enzyme activity in your blood."]

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

Key facts at a glance

LOINC
2549-4
Short code
LDH5 SerPl-cCnc
Synonyms
LDH5 SerPl-cCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
140
Ref high
280
Critical range
— – 1000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 found in many tissues, including the heart, liver, kidneys, muscles, and red blood cells. When cells are damaged, LDH is released into the bloodstream. Different types of LDH (isoenzymes) can indicate where the damage is occurring, though this test alone doesn’t specify the exact tissue.

Why Is LDH Tested?

Doctors may order an LDH test to investigate symptoms like chest pain, fatigue, muscle weakness, or unexplained lab abnormalities. It can also be used alongside other tests to diagnose conditions such as heart attacks, liver disease, anemia, or certain cancers.

Common Conditions Monitored

Elevated LDH levels may suggest conditions like myocardial infarction (heart attack), liver disease, muscle injuries, hemolytic anemia (red blood cell breakdown), or certain types of cancer. Lower levels might be seen in healthy individuals or those with certain metabolic disorders.

Sample Collection and Preparation

This test requires a blood sample drawn from a vein, typically in your arm. The sample is collected in a tube that separates serum or plasma from blood cells. The test may be performed immediately or stored for later analysis depending on the lab’s protocols.

Reference range

Adult: 140-280 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.

Clinical Significance: LDH Levels and Health Implications

Short name

LDH Activity

Frequently asked questions

What Does an Elevated LDH Level Mean?
An elevated LDH level often signals tissue damage or stress. While it doesn’t pinpoint the exact cause, it can prompt further testing to explore potential conditions like heart disease, liver problems, or blood disorders. Always discuss results with your healthcare provider.
How Often Should LDH Be Checked?
The frequency of LDH testing depends on your medical history, symptoms, and ongoing health conditions. Your doctor will determine if regular monitoring is needed, such as for monitoring treatment progress or managing chronic illnesses.
Can LDH Levels Change with Diet or Exercise?
Diet and exercise can indirectly affect LDH levels. Heavy exercise may temporarily increase LDH due to muscle damage, while certain medications or toxins could also influence enzyme activity. Always consider lifestyle factors with your healthcare provider when interpreting results.
  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