LDH (Lactate Dehydrogenase)
Also written as: LD, Lactic acid dehydrogenase
An enzyme in almost every tissue, released into blood when cells are damaged or break down.
What it measures
The level of lactate dehydrogenase, an enzyme involved in energy production that is present in nearly every cell in the body. Because cells release it when they are damaged or destroyed, the blood level works as a general gauge of cell turnover.
Why a doctor orders it
It is used as a broad marker of tissue damage, most often in workups for red cell breakdown (hemolysis), and to follow certain cancers and their treatment. It also gets measured on fluid samples, such as fluid drawn from around the lungs, to help characterize where the fluid came from.
What is generally associated with a higher result
Broadly associated with anything that damages cells: breakdown of red blood cells, liver disease, muscle injury, heart muscle injury, some infections, and some cancers with rapid cell turnover. The test is deliberately non-specific - other results and the clinical picture point at which tissue is the source.
What is generally associated with a lower result
A low LDH is uncommon and usually has no clinical significance. Large doses of vitamin C have been reported to lower it.
Everyday things that move this number
Not every shift in a value reflects disease. These are ordinary factors known to affect this particular measurement:
- Sample handling - red cells breaking open in the tube falsely raise it, one of the most common causes of an unexpected result
- Strenuous exercise shortly before the draw
- Delays in processing the sample
- Intramuscular injections in the days before the draw
Questions to take to your appointment
- Could this be a sample-handling artifact rather than a real rise?
- Which tissue do the other results point to as the source?
- Is this value being followed over time for a specific reason?
Build a printable questionnaire with your own results →
Where to read more
MedlinePlus, from the US National Library of Medicine, publishes patient-facing pages on individual lab tests and is a reliable next stop: medlineplus.gov/lab-tests .
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