Lactate dehydrogenase (often abbreviated LDH) is an enzyme found in almost all body tissues of plants and animals. In humans, this enzyme plays a major role in converting glucose from food into usable energy for cells, KidsHealth reports. Under normal conditions the levels of lactate dehydrogenase in the blood are low, so high levels might indicate one of several medical conditions. The normal range of LDH is between 105 and 333 international units per litre, according to the National Institutes of Health.
A doctor often orders an LDH test to determine if tissue has been damaged. When tissues are damaged by trauma or disease, higher amounts of the LDH enzyme are released into the bloodstream. While an LDH test can determine the presence of tissue damage, further tests often are necessary to assess the severity and location of the damage. An LDH isoenzymes test might be ordered to narrow the source and severity of cellular damage.
Hemolytic anaemia occurs when an abnormal breakdown of red blood cells takes place. Because LDH is abundant in red blood cells, elevated LDH in the bloodstream can be a marker for hemolyisis, a medical term that describes the destruction of red blood cells.
Recent Heart Attack
LDH levels typically rise after people suffer damage to the heart muscle from a heart attack. Usually, the LDH level rises from 24 to 48 hours after a heart attack. then peaks for two to three days and goes back to normal after 10 to 14 days, according to the Florida Agency for Health Care Administration.
Many cancers can raise the LDH level, though an elevated LDH cannot pinpoint a specific type of cancer. Because cancer cells have a high rate of turnover, LDH levels rise due to destroyed cells. LDH tests often are ordered in cancer patients as part of follow-up care to see if treatments are working.
Because LDH is found in the kidneys, liver, heart muscle, brain, lungs and red blood cells, high levels of LDH can indicate many other conditions, including viral meningitis, encephalitis, liver disease, lung disease, kidney disease and muscular dystrophy, to name a few. Certain drugs and strenuous exercise, however, also can elevate LDH levels in the blood. A mishandled blood sample might show up as a false positive for high LDH levels due to ruptured red blood cells.