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Lactate Dehydrogenase (LDH) Activity in Serum/Plasma

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

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

Quick summary

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

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

Key facts at a glance

LOINC
109785-6
Short code
LDH Msmt CSF
Synonyms
LDH Msmt CSF
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Ref low
140
Ref high
280
Critical range
— – 1000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
83615
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Doctors may order LDH testing to check for damage to organs like the heart, liver, or muscles. It can also help identify conditions such as infections, anemia, or certain cancers. LDH levels can rise if tissues are injured or stressed.

What Does the Test Involve?

A blood sample is taken 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.

What Are Common Causes of Elevated LDH?

High LDH levels may occur due to conditions like heart attacks, liver disease, muscle injuries, infections, or blood disorders. It can also be elevated during pregnancy or in response to certain medications.

What Are Common Causes of Low LDH?

Low LDH levels are less common and may occur in rare cases, such as certain genetic disorders or severe liver disease that drastically reduces enzyme production.

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.

LDH is a useful marker for detecting tissue damage or disease activity. Elevated levels often signal underlying issues that require further medical evaluation, such as investigating symptoms of fatigue, chest pain, or unexplained weakness. Doctors use LDH alongside other tests to guide diagnosis and treatment plans.

Short name

LDH Activity

Frequently asked questions

What does a high LDH level mean?
A high LDH level may indicate damage to organs or tissues, such as the heart, liver, or muscles. It can also be associated with infections, blood disorders, or certain cancers. Your doctor will review your symptoms and other test results to determine the cause.
Does LDH change with diet or exercise?
LDH levels can be influenced by muscle activity, such as intense exercise, which may temporarily raise LDH. However, diet alone does not significantly affect LDH levels unless there is underlying organ damage.
Can LDH levels be affected by medications?
Yes, some medications—like certain chemotherapy drugs, antibiotics, or blood thinners—may affect LDH levels. Always inform your healthcare provider about all medications you are taking, as this can help avoid unnecessary testing or changes in treatment.
  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