lactate dehydrogenase (LDH) test, a blood test used to detect levels of lactate dehydrogenase, which is widely distributed throughout the body. Disease or injury to body tissues such as the heart, liver, red blood cells, kidneys, skeletal muscles, brain, and lungs will result in higher-than-normal blood levels. Five separate isoenzymes make up the total LDH, with each body tissue containing a predominance of one or more of these fractions.
