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Lactate Dehydrogenase (LDH) Activity in Serum/Plasma

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

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

Quick summary

["LDH helps doctors identify possible tissue damage or metabolic issues."]

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

Key facts at a glance

LOINC
51516-3
Short code
LDH3 CFr CSF Elph
Synonyms
LDH3 CFr CSF Elph
Category
chemistry
Sample
csf
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
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

What Does LDH Measure?

LDH is an enzyme found in many tissues, including the heart, liver, kidneys, brain, and red blood cells. When cells are damaged, LDH is released into the bloodstream. Measuring LDH activity helps determine the extent of cell injury or disease activity.

Why Might You Need This Test?

Doctors may order LDH testing to investigate symptoms like chest pain, fatigue, muscle weakness, or unexplained lab abnormalities. It’s also used in monitoring conditions such as heart attacks, liver disease, anemia, or certain cancers.

Common Conditions Monitored

LDH is often checked alongside other tests to diagnose or manage conditions like myocardial infarction (heart attack), liver disease (e.g., hepatitis), hemolytic anemia, or metastatic cancer.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is separated into serum or plasma for testing. LDH activity is measured using a specialized lab technique that detects its enzymatic function.

Reference range

Adult: 140-280 U/LN/A

Specimen: csf

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

How high or low are my LDH levels?
While specific reference ranges vary by lab, elevated LDH levels often indicate tissue damage or disease activity. However, normal levels don’t always rule out underlying conditions. Your doctor will interpret results in the context of your symptoms and other tests.
Can lifestyle factors affect LDH levels?
Occasional increases in LDH can occur with intense exercise, dehydration, or certain medications. Chronic conditions like heart disease or liver problems may also influence levels. Discuss any recent changes in activity or medications with your healthcare provider.
What if my LDH levels are abnormal?
If your LDH is elevated, your doctor may recommend further testing (e.g., heart enzymes, liver function tests) or follow-up to investigate possible causes. If levels are low, it may not indicate a problem but could warrant additional evaluation depending on your 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 16, 2026. · Read our editorial policy