Importance of a LDH Blood Test

By Niki | October 12, 2011

In order to know what is LDH blood test, one would need knowledge about what does LDH mean. LDH is known by various names, LD, lactatic dehydrogenase, lactate dehydrogenase, LDH isoenzymes, or total LDH. LDH (consisting of five molecular forms of LDH) is an enzyme found in all cells and tissues of the body. This enzyme is released into the blood once there is trauma or damage to a tissue or organ.

An LDH blood test is performed to detect and determine the extent of tissue disease or damage to the brain, kidney, muscles, liver, and lungs. It is performed in case of bone fractures, anemia, and cancers. This test can be called for if the doctor wants to ascertain or rule out organ disease or damage. LDH tests are also used to determine tissue damage in an accident or injury. As red cells may disintegrate after an artificial valve implant, cardiologists may also call for an LDH test.

Test Normal Range

A doctor recommends a blood test to determine the location and extent of tissue trauma. Isoenzymes levels are studied to pinpoint tissue damage and site of damage for further prognosis. The LDH blood test normal range should be between 48 to 115 IU per liter. Less than 90IU/liter is considered to be normal.

Test Levels

LDH is normally contained within the body cells, and hardly detectable in the blood. After a tissue damage, LDH level increases in the blood. If the LDH level is uncommonly high, then the doctor will call for LDH blood test to identify organs that have been affected. Levels of all five isoenzymes or components of LDH are taken into account when diagnosing LDH blood test results. Regular monitoring of LDH levels is required to observe the status quo of tissue damage or the healing process. The LDH isoenzymes are tissue/organ specific. So the LDH blood test levels help in determining the location of the affected organ and the extent of disease.

The locations of the five isoenzymes are as follows:

  • LDH-1: Germ cells, kidney, red cells
  • LDH-2: Red cells, heart, kidney (smaller amount compared to LDH-1)
  • LDH-3: Lungs, various tissues
  • LDH-4: Lymph nodes, white cells, liver (smaller amount than LDH-5), muscles
  • LDH-5: Skeletal muscles, liver


The LDH blood test results depend on one’s age, gender, and the type of test procedure conducted by a particular laboratory. The ideal or normal range is 105 to 133 IU/L (international units per liter). The result also depends on the body organ or tissue under study. Its location in the body and extent of trauma will also affect the results.