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Lactate Dehydrogenase (LDH) Activity in Serum/Plasma

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

This test measures the activity level of the enzyme lactate dehydrogenase (LDH) in your blood. LDH plays a key role in converting lactate to pyruvate, helping your body produce energy.

Quick summary

["LDH helps diagnose and monitor conditions affecting your heart, liver, muscles, or red blood cells."]

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

Key facts at a glance

LOINC
2546-0
Short code
LDH4 SerPl-cCnc
Synonyms
LDH4 SerPl-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 Does LDH Measure?

LDH is an enzyme found in many tissues, including the heart, liver, kidneys, brain, and red blood cells. When cells are damaged or diseased, LDH levels in your blood can rise. This test helps identify areas of injury or illness by measuring how active LDH is in your serum or plasma.

Why Might You Need This Test?

Doctors may order LDH testing to investigate symptoms like chest pain, unexplained fatigue, muscle weakness, or organ-related issues (such as liver or kidney problems). It can also be used to monitor conditions like heart attacks, infections, anemia, or certain cancers.

Common Conditions Monitored

Elevated LDH levels may signal conditions like heart attacks, liver disease, muscle injuries, or blood disorders. However, LDH alone isn’t diagnostic—it’s often used alongside other tests for a full picture.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The sample is then sent to a lab for analysis. LDH activity is measured using an enzymatic method that detects its ability to convert lactate to pyruvate over time.

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

How often will I need this test?
LDH levels can fluctuate depending on your health status, so your doctor may order this test periodically if you have an ongoing condition (e.g., heart disease, cancer) or symptoms that warrant monitoring.
What do my LDH results mean?
Results alone don’t provide a diagnosis. Your doctor will compare your LDH level to your symptoms, medical history, and other test results to determine if further investigation is needed.
Can lifestyle changes affect LDH levels?
Yes, factors like intense exercise, muscle injuries, or certain medications (e.g., some chemotherapy drugs) can temporarily raise LDH levels. Your doctor will discuss any potential influences with you.
  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