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Serum Lactate Dehydrogenase Activity (LDH)

Published: August 9, 2026Updated: August 17, 2026

This test measures the activity of an enzyme called lactate dehydrogenase (LDH) in your blood. LDH helps convert lactate to pyruvate during energy production.

Quick summary

["LDH helps diagnose conditions affecting cells, such as heart attacks or certain cancers."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
14403-0
Short code
LDH Gast-cCnc
Synonyms
LDH Gast-cCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 1000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84484
SNOMED
302774002
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 is often checked alongside other blood tests to help identify issues like heart damage (e.g., after a heart attack), muscle injuries, liver problems, or certain blood cancers. It can also be used to monitor conditions like anemia or infections.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where the LDH enzyme activity is measured using a specialized test that detects its ability to convert lactate to pyruvate.

What Does a High or Low LDH Level Mean?

High LDH levels may suggest damage to cells in organs like the heart, liver, or muscles. Low levels are less common but can sometimes indicate certain blood disorders or severe infections. Your doctor will interpret results in the context of your symptoms and other tests.

Common Conditions Monitored with LDH

LDH is frequently used to assess conditions such as myocardial infarction (heart attack), liver disease, muscle disorders, or hematologic malignancies (e.g., lymphoma). It can also help track disease progression or response to treatment.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

LDH Activity

Frequently asked questions

Why might my doctor order an LDH test?
Your doctor may order an LDH test if you have symptoms like chest pain, fatigue, unexplained muscle weakness, or signs of organ damage (e.g., nausea, jaundice). It’s also used in monitoring conditions like cancer or infections.
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.
Can lifestyle changes affect LDH levels?
Yes, certain activities like intense exercise, muscle injuries, or chronic conditions (e.g., liver disease) can temporarily raise LDH levels. However, diet alone does not significantly impact LDH unless underlying conditions are present.
  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 17, 2026. · Read our editorial policy