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Lactate Dehydrogenase (LDH) Activity in Serum/Plasma

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

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, muscles, 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
2538-7
Short code
LDH2 SerPl Chem Sepn-cCnc
Synonyms
LDH2 SerPl Chem Sepn-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
chemical-separation
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 often checked to help identify or monitor conditions such as heart attacks, liver disease, muscle injuries, or certain cancers. It can also be useful in diagnosing infections or blood disorders.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm, and sent to a lab. The lab measures how much LDH is present in your serum or plasma using an enzymatic method.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms like chest pain, fatigue, nausea, or unexplained muscle weakness. It may also be part of routine check-ups for certain conditions or after an injury.

What Are Possible Results?

Results are reported as an activity level (units per liter), but exact values can vary by lab. Higher or lower than expected levels may signal underlying health concerns.

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 does an elevated LDH level mean?
An elevated LDH level may indicate damage to tissues where LDH is present, such as the heart, liver, or muscles. Your doctor will consider your symptoms and other test results to determine the cause.
What does a low LDH level mean?
Low LDH levels are less common and may suggest certain genetic conditions or metabolic issues. Your doctor will review your medical history and other test results to understand the significance.
How often should I get this test?
The frequency depends on your health status and reasons for testing. Your doctor will advise you based on your specific situation, such as monitoring chronic conditions or evaluating symptoms.
  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