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Lactate Dehydrogenase (LDH) Activity in Serum/Plasma

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

This test measures the amount of an enzyme called lactate dehydrogenase (LDH) in your blood. LDH helps break down lactate into less harmful substances and is found in many tissues, including the heart, liver, and muscles.

Quick summary

["LDH helps your body manage energy and can signal potential damage to organs."]

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

Key facts at a glance

LOINC
53742-3
Short code
L pneumo 2+3+4+5+6+8 Ab Ser Ql
Synonyms
L pneumo 2+3+4+5+6+8 Ab Ser Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 levels can help doctors diagnose or monitor conditions affecting the heart, liver, muscles, kidneys, red blood cells, or lungs. For example, high LDH might suggest muscle injury, certain cancers, or infections.

Why Might You Need This Test?

Your doctor may order LDH testing if you have symptoms like fatigue, chest pain, unexplained bruising, or signs of organ damage. It’s also used during cancer screenings or to check for complications from treatments.

How Is the Test Done?

A blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where LDH activity is measured using an automated test that detects its enzyme function.

What Do Results Mean?

Results are reported as a numerical value representing LDH activity. While reference ranges vary by lab, elevated levels may indicate tissue damage or disease, while normal levels suggest healthy enzyme function.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

LDH Serum/Plasma

Frequently asked questions

What causes LDH levels to be higher than usual?
High LDH can result from conditions like muscle injuries (e.g., from exercise or trauma), heart attacks, liver disease, blood disorders, or infections. Some cancers (e.g., lymphoma) may also raise LDH levels.
How long does it take to get results?
Test results are typically available within 1–3 business days, depending on lab processing times. Your doctor will discuss the results with you during your follow-up visit.
Can lifestyle changes affect LDH levels?
Yes, certain activities like intense exercise, alcohol consumption, or muscle injuries can temporarily raise LDH. However, chronic conditions like heart disease or liver problems require medical evaluation, not just lifestyle adjustments.
  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