This is a blood test that measures the level of lactic dehydrogenase (LDH) in your body. LDH is an enzyme, or catalyst, found in many different tissues in your body. These include your red blood cells, skeletal muscles, kidneys, brain, and lungs.ou may also have a lactate dehydrogenase isoenzyme test. Your total LDH is made up of 5 isoenzymes numbered LDH-1 through LDH-5. The concentration of each isoenzyme depends on the tissue. For example, LDH-1 and LDH-2 are found mainly in heart tissue. LDH-5 is found mostly in the liver.