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Lactate Dehydrogenase (LDH) Activity in Serum or Plasma

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

This test measures the activity level of the enzyme lactate dehydrogenase (LDH), which plays a key role in converting lactate to pyruvate during energy production in cells. LDH is found in many tissues, including the heart, liver, kidneys, and red blood cells.

Quick summary

["LDH helps doctors assess damage to organs or tissues and monitor certain conditions."]

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

Key facts at a glance

LOINC
57664-5
Short code
LDH Smn-cCnc
Synonyms
LDH Smn-cCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
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
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 tests to diagnose or monitor conditions like heart attacks, liver disease, muscle injuries, anemia, or certain cancers. Elevated LDH levels may suggest damage to cells where the enzyme is present, though it can also be influenced by other factors like exercise or certain medications.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The blood is then sent to a lab where LDH activity is measured using an enzymatic method. No special preparation is needed, but you may want to avoid strenuous activity for a few hours before the test.

Why Might LDH Levels Be Checked?

Your healthcare provider may order LDH testing if you have symptoms like chest pain, fatigue, nausea, or unexplained bruising/swelling. It can also be part of routine check-ups or follow-up care for known conditions.

What Could Affect LDH Levels?

Several factors can influence LDH levels, including recent exercise, certain medications, infections, or dehydration. High levels may also occur in conditions like hemolytic anemia (red blood cell breakdown) or severe infections.

Reference range

Adult: 140-280 U/LN/A

Specimen: serum

No special preparation required. Inform provider of any chest pain or symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

LDH Activity

Frequently asked questions

What does an elevated LDH level mean?
An elevated LDH level may indicate damage to cells where the enzyme is present, such as the heart, liver, or muscles. It can also be seen in conditions like anemia, infections, or certain cancers. Your doctor will consider your symptoms and other test results to determine the cause.
What does a low LDH level mean?
Low LDH levels are less common and may suggest certain metabolic disorders, vitamin deficiencies (like folate or B12), or rare genetic conditions. Your doctor will review your medical history and other test results to understand why your LDH is low.
Do I need to prepare for this test?
No special preparation is needed, but avoid strenuous activity for a few hours before the test. If you’re on certain medications or have a condition that might affect your blood, let your healthcare provider know.
  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