The LDH test is a blood test that measures the level of Lactate Dehydrogenase, an enzyme present in nearly every cell of the body including the liver, heart, kidneys, muscles, lungs, and red blood cells. LDH plays a fundamental role in energy production, catalysing the conversion of lactate to pyruvate as part of cellular metabolism. Under normal conditions, LDH is contained within cells and only small amounts circulate in the bloodstream. When cells are damaged, destroyed, or under significant stress, LDH is released into the blood, causing levels to rise.
Because LDH is found in virtually all tissues, it is a broad marker of cellular injury rather than organ-specific damage. Its clinical value lies in its sensitivity as a general indicator of tissue destruction across multiple conditions including haemolytic anaemia, liver disease, heart attack, kidney disease, muscle injury, and various cancers. In oncology particularly, LDH has emerged as one of the most important prognostic markers, with elevated levels in cancer patients reflecting tumour burden, aggressive disease biology, and poorer treatment outcomes. In India, LDH is increasingly prescribed not only in acute illness but as part of cancer staging, lymphoma workup, and monitoring of haematological malignancies. The test involves a simple blood draw completed in under five minutes.