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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 energy production and cell health. LDH levels can help identify conditions affecting tissues where cells are damaged or stressed.

Quick summary

["LDH helps diagnose and monitor conditions linked to tissue injury or metabolic processes."]

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

Key facts at a glance

LOINC
5921-2
Short code
LDH Dial fld-cCnc
Synonyms
LDH Dial fld-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 Is LDH Used For?

LDH is commonly used to assess damage to organs such as the heart, liver, kidneys, lungs, and muscles. Elevated levels may suggest conditions like heart attacks, infections, or certain cancers. It can also be part of routine monitoring for chronic diseases.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is then sent to a lab where LDH activity is measured using an enzymatic method to detect its presence and concentration in your serum or plasma.

What Might Affect LDH Levels?

Several factors can influence LDH levels, including recent exercise, certain medications, infections, or underlying health conditions. For example, strenuous activity can temporarily raise LDH, while certain blood disorders or cancers may lead to consistently elevated levels.

When Might You Need This Test?

Your healthcare provider may order an LDH test if you have symptoms like chest pain, unexplained fatigue, or signs of organ damage. It’s also used in diagnosing conditions like myocardial infarction (heart attack), liver disease, or to monitor treatment progress in diseases like leukemia.

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

Why did my doctor order this test?
Your doctor may have ordered LDH testing to investigate symptoms like pain, fatigue, or lab results that suggest tissue damage, infections, or other health concerns. LDH can help pinpoint which organs or systems may be affected.
What do my LDH results mean?
Results are typically compared to a baseline or reference range provided by your lab. While elevated LDH often signals tissue injury, a single test result alone isn’t diagnostic. Your doctor will consider your symptoms, medical history, and other test results to interpret the meaning.
Can I take anything special before this test?
No special preparations are needed, but avoid strenuous exercise 24 hours before the test, as it may temporarily affect results. If you’re on medications, let your healthcare provider know before the test.
  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