The LDH Serum test is a broad but important indicator of tissue health. It measures the level of Lactate Dehydrogenase, an enzyme found in almost all body cells, in your bloodstream. When cells are damaged or destroyed, they release LDH. An elevated level signals that there is tissue damage somewhere in the body. While not specific, it is a vital marker for investigating a wide range of conditions, from hemolytic anemia to muscle injury. This simple blood test acts as a general alarm, alerting your doctor that further investigation is needed.