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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 muscle, liver, heart, or red blood cells.

Quick summary

["LDH helps diagnose damage to organs or tissues and monitor certain diseases."]

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

Key facts at a glance

LOINC
60020-5
Short code
LDH Prt P to L-cCnc
Synonyms
LDH Prt P to L-cCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0.8
Ref high
1.2
Critical range
— – 5 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
reaction-pyruvate-to-lactate
CPT
85610
SNOMED
396252006
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?

Your healthcare provider may order an LDH test to check for conditions like heart attacks, liver disease, muscle injuries, or red blood cell disorders. It can also help evaluate symptoms such as fatigue, chest pain, or unexplained bruising.

What to Expect Before the Test

No special preparation is usually needed. You may fast if instructed, but this is not always required. Bring any medications you’re taking to your appointment.

How the Test Works

A blood sample is drawn from a vein, usually in your arm. The blood is sent to a lab where LDH activity is measured using an enzymatic method to detect how well the enzyme functions.

What the Results Mean

Results are reported as an activity level (units per liter), but exact reference ranges can vary by lab. Elevated levels may suggest tissue damage or disease, while lower levels might indicate certain genetic conditions.

Reference range

INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A

Specimen: serum

Inform your healthcare provider if you are taking blood thinners. No special preparation required.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

LDH Activity

Frequently asked questions

What causes elevated LDH levels?
Elevated LDH can result from conditions like heart attacks, liver disease, muscle injuries (e.g., from exercise or trauma), certain cancers, infections, or blood disorders. It may also appear in people with anemia or hemolytic conditions.
What causes low LDH levels?
Low LDH levels are less common but can occur in genetic disorders affecting LDH production, severe liver disease (in some cases), or rare metabolic conditions. Your doctor will consider other factors when interpreting results.
Can LDH levels change over time?
Yes, LDH levels can fluctuate depending on underlying health conditions, treatments, or recovery from injuries. Follow-up tests may be needed to monitor trends, especially if you have ongoing symptoms or a known condition affecting LDH.
  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