Lactate dehydrogenase (LDH) is an enzyme that helps facilitate the process of turning sugar into energy for your cells to use. LDH is present in many kinds of organs and tissues throughout the body, including the liver, heart, pancreas, kidneys, skeletal muscles, brain, and blood cells.When illness or injury damages your cells, LDH may be released into the bloodstream, causing the level of LDH in your blood to rise.aking an LDH Test. LDH levels are normally measured using a blood draw. Occasionally, LDH levels may be measured using urine or cerebrospinal fluid. In adults, blood is taken from a vein at the inner elbow or the back of the hand.