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LDH

LFT Biomarker

Sample Needed

Collection Type: Blood

Body System

Related System: LFT

Overview

Lactate dehydrogenase (LDH) is an enzyme present in nearly all body tissues (liver, heart, muscle, red blood cells, kidneys, lungs). A serum LDH test measures the total circulating enzyme released when cells are damaged or destroyed. It is a nonspecific marker of tissue injury—elevations can signal liver disease (hepatitis, cirrhosis, hepatic necrosis) but also hemolysis, myocardial infarction, muscle injury, pulmonary embolism, and some cancers. Symptoms prompting testing include jaundice, abdominal pain, dark urine, unexplained fatigue, chest pain, shortness of breath, or signs of hemolytic anemia. Levels vary with age (newborns higher), recent exercise, pregnancy, and may be slightly higher in males; interpretation requires clinical context and other tests.

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: included in LFT (liver function tests) or as part of a tissue-injury panel.
Symptoms: jaundice, abdominal pain, unexplained anemia, chest pain, muscle pain, dyspnea.
Use: helps detect/monitor liver damage, hemolysis, muscle injury, malignancy, or ischemia.
Abnormal reasons: cell/tissue breakdown from disease, hemolysis, infarction, infection, cancer, strenuous exercise, or sample hemolysis.
Biological meaning: elevated LDH = increased cell destruction; low LDH is rarely clinically important.
Family history of hemolytic disorders, muscular diseases, or hereditary enzyme defects may prompt testing.

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Understanding Test Results

Mild elevation (up to ~2× ULN; ~280–560 U/L): suggests minor or early tissue injury—mild hepatitis, minor hemolysis, recent strenuous exercise, or early infection.
Correlate with ALT/AST, bilirubin, CK.
Moderate elevation (~2–5× ULN; ~560–1,400 U/L): indicates more significant tissue damage—acute hepatitis, substantial hemolysis, pneumonia, pulmonary embolism, myocardial injury; further evaluation and imaging/tests warranted.
Marked elevation (>5× ULN; >1,400 U/L): seen with severe conditions—massive hepatic necrosis, severe rhabdomyolysis, widespread malignancy, or profound hemolysis; often urgent workup required.
Very low values: uncommon and usually not clinically meaningful; rare genetic LDH deficiency can cause symptoms like exercise-induced myoglobinuria.
Note: hemolysis in the blood sample can falsely raise LDH.
Isoenzyme fractionation or complementary tests (ALT/AST, CK, troponin, bilirubin, haptoglobin) help localize the source.
Always interpret alongside clinical findings.

Normal Range

140-280 U/L

FAQs

Q: What does a high level of LDH mean?

A: High lactate dehydrogenase (LDH) indicates cell or tissue damage because LDH is released into blood when cells break down. Elevated LDH is non‑specific and may reflect hemolysis, liver or muscle injury, heart attack, infections, certain cancers, or inflammatory conditions. It helps detect and monitor disease but requires correlation with symptoms, other labs and imaging; consult a clinician for interpretation and further testing.

Q: Is LDH a tumor marker?

A: LDH (lactate dehydrogenase) is not a specific tumor marker. It’s an enzyme released with cell injury, so levels rise in many conditions infection, liver disease, hemolysis, heart damage and cancer. Elevated LDH can reflect tumor burden or prognosis in some cancers (e.g., lymphoma, melanoma, germ-cell tumors), but it’s nonspecific and must be interpreted with clinical context and other investigations.

Q: What is LDH and its function?

A: Lactate dehydrogenase (LDH) is a ubiquitous enzyme that catalyzes the reversible conversion of pyruvate to lactate while regenerating NAD+ from NADH. It supports anaerobic glycolysis and cellular energy production when oxygen is low. LDH is abundant in heart, liver, muscle, kidney and red blood cells; elevated blood levels indicate tissue damage, hemolysis, inflammation, or certain cancers.

Q: Is LDH a cardiac marker?

A: LDH (lactate dehydrogenase) is a general marker of tissue injury that can rise after heart damage, but it is not a specific cardiac marker. LDH isoenzyme patterns (LDH‑1 predominance) may suggest myocardial injury, yet troponins are far more sensitive and specific for diagnosing heart attack. LDH’s delayed rise and low specificity limit its clinical usefulness for acute cardiac diagnosis.

Q: What cancers have high LDH levels?

A: High LDH levels occur in many cancers, most commonly in aggressive hematologic malignancies (acute leukemia, high‑grade non‑Hodgkin lymphoma), germ cell and testicular tumors, metastatic melanoma, and advanced solid tumors such as lung, pancreatic, liver, renal, ovarian, colorectal and breast cancers. Elevated LDH often reflects high tumor burden, rapid cell turnover, or metastasis and has prognostic value.

Q: What is the treatment for high LDH?

A: Treatment focuses on addressing the underlying cause rather than the LDH level itself. Manage infections, liver disease, hemolysis, ischemia or malignancy with appropriate antibiotics, antivirals, liver-supportive care, transfusion, anticoagulation, chemotherapy or surgery as indicated. Supportive measures include oxygen, hydration, stopping offending drugs, and repeat monitoring. Work with your clinician to diagnose the cause and tailor therapy.