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Lactate Dehydrogenase (LDH) Activity in Serum/Plasma

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

This test measures the activity of the enzyme lactate dehydrogenase (LDH), which plays a role in energy production in cells. It helps identify conditions affecting cell damage or metabolism.

Quick summary

["LDH helps diagnose conditions linked to cell injury or metabolic dysfunction."]

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

Key facts at a glance

LOINC
51520-5
Short code
LDH5 CFr Prt Elph
Synonyms
LDH5 CFr Prt Elph
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
140
Ref high
280
Critical range
7.2 N/A – 7.6 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
electrophoresis
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

Why Is This Test Done?

Doctors may order LDH testing to investigate symptoms like fatigue, muscle pain, or organ dysfunction. It can also be used alongside other tests to assess conditions such as heart attack, liver disease, muscle disorders, or certain cancers.

Common Conditions Monitored

High LDH levels may suggest damage to cells in the heart, liver, kidneys, lungs, or muscles. Low levels are less commonly significant but may indicate certain metabolic or genetic conditions.

Sample Collection and Preparation

A blood sample is taken from a vein, usually in the arm. The sample is collected in a tube and sent to the lab for analysis. LDH activity is measured using an enzymatic method to detect its presence and activity in the serum or plasma.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to avoid strenuous activity or certain medications for a short time before the test, depending on your doctor’s instructions.

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.

Clinical Significance: LDH Levels and Health Implications

Short name

LDH Activity

Frequently asked questions

How long will results take to return?
Results are typically available within 24 to 48 hours, depending on your lab’s processing schedule. Your doctor will discuss the findings with you during your follow-up visit.
Can I eat or drink before this test?
For most LDH tests, fasting is not required. However, always follow your healthcare provider’s specific instructions, as some labs may have guidelines for dietary restrictions.
What if my LDH level is elevated?
If your LDH level is elevated, your doctor may recommend further testing to determine the underlying cause, such as checking for heart damage, liver issues, or other conditions affecting your cells.
  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