Lactate dehydrogenase (LDH) is an enzyme found in nearly all body tissues. It plays a crucial role in the conversion of lactate to pyruvate in the process of cellular respiration. Elevated or decreased LDH levels can indicate various medical conditions.

LDH is released into the bloodstream when cells are damaged or destroyed. Therefore, measuring LDH levels can help detect and monitor tissue damage or disease in various organs.

Historically, LDH was used to diagnose myocardial infarction. Although now largely replaced by more specific markers like troponin, LDH levels can still be elevated in cases of heart muscle damage.

Elevated LDH levels can indicate liver damage from conditions like hepatitis, cirrhosis or liver metastases from cancers.

In haemolytic anaemia, the destruction of red blood cells releases LDH into the bloodstream, leading to elevated levels.

Elevated LDH levels can be seen in various cancers, including lymphomas, leukaemias, and solid tumours. LDH can serve as a prognostic marker, where higher levels often indicate more aggressive disease or greater tumour burden.  LDH levels can be used to monitor the effectiveness of cancer treatment. Decreasing levels may indicate a positive response to therapy.