The lactate dehydrogenase (LDH) test looks for signs of damage to the body's tissues. This test measures the level of lactate dehydrogenase (LDH) in blood or other body fluids. Learn how the lactate dehydrogenase (LDH or LD) test is used, when an LD test is ordered, and what the results of an LD test might mean. Lactate dehydrogenase (also called lactic acid dehydrogenase, or LDH) is an enzyme found in almost all body tissues. Lactate dehydrogenase is an enzyme that helps turn sugar into energy for your cells. Lactate dehydrogenase (LDH) is a protein that helps produce energy in the body.