LDH is an energy enzyme present in nearly every cell, so it leaks into blood whenever tissue anywhere is damaged. It is unspecific by design, but its level and trend carry real prognostic weight in blood cancers, severe infections and hemolysis.
Standard range versus optimal range
| Framework | LDH value | Source |
|---|---|---|
| Standard lab reference | about 140-280 U/L | Common laboratory range |
| Notable elevation | above 2 times the upper limit | Clinical practice |
When it runs high
High LDH reports cell breakdown somewhere in the body, and the magnitude matters. Mild rises follow exercise, hemolysis or liver congestion, moderate rises accompany pneumonia and kidney injury, and very high values raise concern for aggressive blood cancers or widespread tissue death.
- Hemolysis, including from a difficult blood draw
- Lymphoma, leukemia and other malignancies with high cell turnover
- Liver congestion or hepatitis
- Muscle injury and intense training
- Pneumonia, sepsis and severe infections
- Heart attack, historically, now replaced by troponin
When it runs low
Low LDH is not clinically meaningful and needs no action. A very rare inherited LDH deficiency affects muscle energy metabolism but is not picked up through routine testing.
- Normal variation
The universal damage reporter
LDH converts lactate to pyruvate in the energy machinery of essentially every cell, which is why its appearance in blood means cells are breaking down but says nothing about where. That unspecificity once made it a cancer screening hope, and it failed at that job. Where LDH truly shines is prognosis and tracking, because its level mirrors the pace of cell turnover in diseases already diagnosed.
Where the number still earns its place
In lymphoma, LDH is part of the international prognostic index and rises with tumor burden. In hemolytic anemia it climbs alongside low haptoglobin and high indirect bilirubin, forming the classic triad. During severe infections including COVID-19 it tracked disease severity, and in testicular cancer it remains an official tumor marker. The trend matters more than any single value, a doubling over weeks means far more than a stable mild elevation.
The most common false alarm
Rough handling of a blood sample breaks red cells in the tube and releases their LDH, producing a falsely high result that fools nobody once the lab flags hemolysis. Intense exercise in the days before a draw does the same honestly. An isolated mild elevation with a normal repeat and a normal blood count rarely needs further pursuit.
Related calculators
Related biomarkers ALT · AST · Total bilirubin