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Plasma or Serum Lactate Dehydrogenase Activity (LDH)

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

This test measures the activity of the enzyme lactate dehydrogenase (LDH) in your blood. LDH helps your body convert lactate to pyruvate and is found in many tissues, including the heart, liver, and muscles.

Quick summary

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

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

Key facts at a glance

LOINC
50509-9
Short code
LH sp1 SerPl-aCnc
Synonyms
LH sp1 SerPl-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
1.5
Ref high
9
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
83002
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 Does LDH Measure?

LDH is an enzyme that plays a role in energy production. It’s present in high levels in cells that are damaged or stressed, such as those in the heart, liver, kidneys, lungs, and red blood cells. Your body releases LDH into the bloodstream when these cells break down.

Why Is LDH Tested?

Doctors may order an LDH test to investigate symptoms like chest pain, fatigue, or unexplained bruising. It can also help identify conditions such as heart attacks, liver disease, anemia, or infections.

When Might You Need This Test?

You might need an LDH test if you have symptoms like persistent fatigue, muscle weakness, or signs of organ damage. It’s also used during follow-ups for known conditions like heart disease, cancer, or blood disorders.

What Happens During the Test?

A healthcare provider will draw blood from a vein in your arm. The blood sample is then sent to a lab for testing. The results help determine if your LDH levels are within normal ranges or if further investigation is needed.

Reference range

Follicular: 1.5-9.0 mIU/mLN/A

Specimen: serum

For females: inform if menstrual cycle status. For certain tests, timing within menstrual cycle may matter.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

LDH Test

Frequently asked questions

How often should I get an LDH test?
LDH tests are often ordered as part of a broader evaluation, such as during a routine checkup, for symptoms, or to monitor a known condition. Your doctor will decide how often you need testing based on your health status and medical history.
What do my LDH results mean?
Elevated LDH levels may indicate tissue damage or disease, but they can also be influenced by factors like exercise, certain medications, or dehydration. Your doctor will discuss the results with you and may recommend additional tests if needed.
Can LDH levels change over time?
Yes, LDH levels can fluctuate depending on your health, activity level, and underlying conditions. Regular monitoring may be necessary if you have a chronic illness or are undergoing treatment for a condition that affects LDH production.
  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