Chemistry / Electrolytes
Lactate dehydrogenaseLDH
Cytosolic enzyme released from any injured cell; nonspecific marker of cell turnover or hemolysis.
Sample
Serum
Clinical reference range
140 to 280 U/L
Adult
Conv: 140–280 U/L
Biology
What it measures
Catalyzes pyruvate ↔ lactate. Five isoenzymes; LDH-1/2 in heart and RBCs, LDH-5 in liver/skeletal muscle.
Clinical use
Why we order it
Hemolysis (with haptoglobin), tumor lysis monitoring, lymphoma/germ-cell tumor staging, PJP prognostic marker.
Differential
Causes of abnormal values
Causes of HIGH
- ↑Hemolysis (in vivo or hemolyzed sample)
- ↑Hepatic injury
- ↑Tumor lysis
- ↑Lymphoma, germ-cell tumors
- ↑Megaloblastic anemia (markedly elevated)
- ↑Pulmonary embolism
- ↑Rhabdomyolysis
Pitfalls
Pre-analytic & interpretation traps
- !Hemolyzed specimen falsely elevates LDH up to 30× — always confirm sample integrity before acting on a high value.
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