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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 and vice versa. LDH is found in many tissues, including the heart, liver, kidneys, and red blood cells.

Quick summary

["LDH helps diagnose and monitor conditions affecting these organs."]

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

Key facts at a glance

LOINC
56759-4
Short code
Deprecated LDH Smn L to P-cCnc
Synonyms
Deprecated LDH Smn L to P-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
Method
reaction-lactate-to-pyruvate
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 Is This Test Done?

Doctors may order LDH testing to investigate symptoms like chest pain, shortness of breath, or unexplained fatigue, which could suggest heart, liver, or muscle damage. It’s also used to monitor conditions like heart attacks, liver disease, or certain cancers.

What Does a High or Low LDH Level Mean?

Elevated LDH levels may indicate damage to cells in organs like the heart, liver, or lungs. Low levels are less common but could suggest certain blood disorders or severe muscle wasting. Your doctor will consider your symptoms and other test results to interpret the results.

Common Conditions Linked to LDH Levels

High LDH is often seen in conditions such as myocardial infarction (heart attack), liver disease, certain cancers (like lymphoma), or severe infections. It can also appear in muscle disorders or blood disorders like hemolytic anemia.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. You may feel a small pinch, but it usually doesn’t cause discomfort. The sample is sent to a lab where the LDH enzyme activity is measured using an automated analyzer.

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.

◆Associated findings1

Short name

LDH Activity

Frequently asked questions

What Are the Normal Results?
There is no single reference range that applies universally, as it can vary slightly by lab and patient demographics. Your doctor will compare your results to your specific lab’s reference values and consider your overall health and medical history.
How Long Does It Take to Get Results?
Results are typically available within 24 to 48 hours, depending on lab processing times. Your doctor will contact you once the results are ready, either through a phone call or a follow-up appointment.
Can I Eat or Drink Before This Test?
You can usually eat and drink normally before this test unless your doctor has specific instructions. Fasting is not required for LDH testing.
  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