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Lactate Dehydrogenase (LDH) Activity in Serum/Plasma

Published: August 9, 2026Updated: August 16, 2026

This test measures the activity of the enzyme lactate dehydrogenase (LDH), which plays a role in energy production in cells. It helps identify conditions affecting cell damage or disease processes.

Quick summary

["LDH helps doctors assess tissue damage or metabolic health."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
51508-0
Short code
LDH1 CFr Plr Elph
Synonyms
LDH1 CFr Plr Elph
Category
chemistry
Sample
fluid
Container
Sterile tube
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
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Doctors may order an LDH test to investigate symptoms like fatigue, muscle weakness, or unexplained pain, which could suggest conditions such as heart attack, muscle disorders, liver disease, or certain cancers. It can also be part of routine monitoring for conditions like anemia or infections.

What Does an LDH Test Tell Us?

LDH levels can rise when cells are damaged, releasing the enzyme into the bloodstream. Elevated levels may indicate conditions like heart attacks, muscle injuries, liver disease, or certain cancers. However, results alone don’t diagnose a specific condition—your doctor will consider symptoms and other test results.

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 needed, but fasting may be advised depending on your doctor’s instructions.

What Are Common Results?

Results are reported as the activity level of LDH in units per liter (U/L), but reference ranges vary by lab and may not be provided to you. Elevated LDH is often noted, but it’s not a standalone diagnosis.

Reference range

Adult: 140-280 U/LN/A

Specimen: fluid

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 causes high LDH levels?
High LDH levels can result from conditions damaging cells, such as heart attacks, muscle injuries, liver disease, certain cancers, or infections. It may also be elevated during pregnancy or with certain blood disorders.
What causes low LDH levels?
Low LDH levels are less common but may occur in rare genetic disorders or with certain medications. Your doctor will review your results in the context of your overall health.
How long does it take to get results?
Results are typically available within 24 to 48 hours, depending on your lab’s processing time. Your doctor will discuss the findings with you during your follow-up visit.
  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 16, 2026. · Read our editorial policy