What does my lactate dehydrogenase (LD) level mean?

What Does My Lactate Dehydrogenase (LD/LDH) Level Mean?

Your LDH level is a nonspecific marker of tissue damage or cellular turnover that requires interpretation within your specific clinical context—elevated levels can indicate anything from benign conditions like strenuous exercise to serious diseases like cancer, heart attack, liver disease, hemolysis, or severe infections. 1

Understanding LDH as a Diagnostic Tool

LDH is an enzyme found in nearly all body tissues, with highest concentrations in the heart, liver, skeletal muscle, kidneys, and red blood cells. 2, 3 When cells are damaged or break down, LDH leaks into your bloodstream, causing elevated levels. 3

The key limitation: LDH elevation alone is nonspecific and cannot pinpoint a specific diagnosis. 1 The clinical significance depends entirely on:

• The degree of elevation: Mild elevations (<5× upper limit of normal) are most commonly benign, while severe elevations (>10× normal) carry higher mortality risk 1
• Your symptoms and medical history
• Other laboratory findings
• Imaging results when applicable

Common Causes of Elevated LDH

Benign and Temporary Causes

• Strenuous exercise can temporarily elevate LDH due to muscle damage 1
• Hemolyzed blood samples (improper specimen handling) falsely elevate results 1, 4
• Liver disease of various etiologies 1
• Myocardial infarction (heart attack) 1
• Kidney disease 1
• Infections 1

Serious Medical Conditions

• Hemolysis (red blood cell breakdown), including from mechanical circulatory support devices 1
• Heart failure, particularly in patients with mechanical support 1
• Preeclampsia in pregnancy 1
• Severe acute pancreatitis: LDH is used alongside other markers to predict severity 5

Cancer-Related Elevations

LDH serves as an important tumor marker in specific cancers:

• Testicular germ cell tumors: Used for diagnosis, prognosis, and treatment monitoring; LDH >2.5× upper limit of normal indicates worse prognosis with 3-year progression-free survival of 75-80% versus 92-93% for normal LDH 1
• Osteosarcoma: Elevated LDH correlates with metastatic disease; 5-year disease-free survival is 39.5% with high LDH versus 60% with normal values 1
• Melanoma: Elevated LDH is incorporated into stage IV classification as a key prognostic factor 1
• Multiple myeloma: Helps assess tumor burden 1
• Lymphomas and leukemias: Particularly Burkitt's lymphoma and B-cell ALL carry highest risk for extreme elevation 1

Pleural Effusion Diagnosis

LDH is a key component of Light's criteria to distinguish exudative from transudative pleural effusions:

• Pleural fluid LDH/serum LDH ratio >0.6 indicates exudate 1
• Pleural fluid LDH >2/3 the upper limit of normal serum LDH indicates exudate 1

How to Interpret Your Result

Step 1: Exclude Artifact

First, ensure the sample wasn't hemolyzed, as this is the most common cause of spurious elevation. 1, 4 Your doctor should verify proper specimen handling.

Step 2: Assess the Degree of Elevation

• Mild elevation (<5× upper limit): Most commonly benign causes 1
• Moderate elevation (5-10× upper limit): Requires clinical correlation
• Severe elevation (>10× upper limit): Associated with higher mortality and requires urgent evaluation 1

Step 3: Consider Clinical Context

Your doctor will interpret LDH alongside:

• Your symptoms: Chest pain, shortness of breath, abdominal pain, jaundice, etc.
• Other laboratory tests: Liver enzymes, kidney function, complete blood count, specific tumor markers if cancer suspected 1
• Imaging studies when indicated
• Medical history: Known cancer, heart disease, pregnancy status, recent exercise 1

Step 4: Additional Testing When Needed

LDH isoenzyme testing is NOT routinely recommended, even in cancer diagnosis where total LDH has established value. 4 Total LDH provides sufficient clinical information in virtually all scenarios. 4

Important Caveats

• Do not rely on LDH alone for diagnosis or treatment decisions 1
• Rising LDH after cancer treatment usually indicates progressive disease requiring salvage therapy 1
• In tumor lysis syndrome, LDH elevation reflects tumor burden and is the main predictor for developing this complication 1
• Medication review is essential, as drug-induced liver injury can cause mild elevations 1

What You Should Do Next

Discuss your specific result with your healthcare provider, who will interpret it in the context of:

• Why the test was ordered
• Your complete clinical picture
• Whether additional testing is needed
• Whether any intervention is required

LDH is a signpost, not a diagnosis—it tells your doctor that something may be happening in your body that requires further investigation based on your individual circumstances. 1, 3