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Serum or Plasma Lactate Dehydrogenase (LDH) Activity

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

This test measures the activity of the enzyme lactate dehydrogenase (LDH) in your blood. LDH helps convert lactic acid into pyruvate, which your body uses for energy.

Quick summary

["LDH levels can help identify conditions affecting your cells, such as damage or disease."]

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

Key facts at a glance

LOINC
74739-4
Short code
Deprecated S agalactiae hsp60 Bld Pos Ql Prb Mag
Synonyms
Deprecated S agalactiae hsp60 Bld Pos Ql Prb Mag
Category
coagulation
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
probe-mag-capture
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order an LDH test to check for signs of certain health issues, such as heart problems, muscle injuries, liver disease, or blood disorders. It can also help diagnose conditions like anemia, infections, or cancers.

What Does It Measure?

LDH is found in many tissues, including the heart, liver, kidneys, muscles, and red blood cells. Elevated LDH levels may suggest damage or disease in these areas, though it can be hard to pinpoint exactly where the problem is.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. The blood is then sent to a lab where the LDH activity is measured using an enzymatic method.

What Are Common Results?

Results are typically reported in units per liter (U/L) or millunits per milliliter (mU/mL). Your results will be compared to a reference range provided by your lab, which can vary slightly by lab.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: LDH Levels Can Indicate Underlying Conditions

Short name

LDH Test

Frequently asked questions

What Causes Elevated LDH Levels?
Elevated LDH levels can occur due to various conditions, including but not limited to, muscle injuries or strains, liver disease, heart attacks, certain cancers (like lymphoma or leukemia), anemia, infections, or blood disorders. LDH can also rise during pregnancy or with certain medications.
What Causes Low LDH Levels?
Low LDH levels are less common and may occur in certain genetic conditions or in people with very low red blood cell counts. It’s important to discuss any concerns with your healthcare provider.
How Often Should I Get This Test?
Your healthcare provider will determine the frequency of LDH testing based on your medical history, symptoms, and specific health needs. Regular monitoring may be recommended if you have a known condition that affects LDH levels.
  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