At a glance

Also known as

LDH; lactate dehydrogenase; total LD; total LDH; LD isoenzymes; LDH isoenzymes

Why get tested?

To help identify tissue damage in the body, and to monitor its progress.

When to get tested?

Along with other tests, when your doctor suspects that you have an acute or chronic condition that is causing tissue or cellular destruction and they want to identify and monitor the problem.

Sample required?

A blood sample drawn from a vein in your arm

Test preparation needed?

None

What is being tested?

Lactate dehydrogenase (LD) is an enzyme that is found in cells throughout the body.

Only a small amount of LD is usually detectable in the blood. However, when cells are damaged or destroyed, they release LD into the bloodstream, causing blood levels to rise. For this reason, LD is used as a general marker of injury to cells. This also happens when blood cells are destroyed in the bloodstream, such as in a form of anaemia known as haemolytic anaemia.

In the past, special tests were done to work out what type of tissue the LD was released from. These tests, known as `LD isoenzymes’ are not done routinely any more because there are better tests available.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

The main use for LD is as a general sign of damage within the body, including muscle damage, liver damage, blood cell damage and cancers. In the past, LD was used to help diagnose and monitor myocardial infarctions (heart attacks) but it has been replaced by a better test, troponin.

In people with progressive conditions, including melanoma, the doctor may ask for LD to be tested at regular intervals to monitor the progress of a condition.

When is it requested?

LD may be used as a screening test when your doctor suspects some kind of tissue damage. If the LD is high the doctor may use other tests such as CKALT and AST to help pinpoint the organs involved. Once the problem is diagnosed, LD levels may be tested at regular intervals to monitor its progress.

What does the test result mean?

Looking for reference ranges?

High levels of LD usually indicate some type of tissue damage. Usually LD levels will rise as the cell destruction begins, peak after some time period and then begin to fall. For instance, when someone has a heart attack, blood levels of total LD will rise within 24 to 48 hours, peak in 2 to 3 days, and return to normal in 10 to 14 days.

Elevated levels of LD may be seen with:

  • Anaemias including haemolytic anaemia
  • Pernicious anaemias (megaloblastic anaemia)
  • Infections including infectious mononucleosis (glandular fever), tuberculosis and serious fungal infections
  • Intestinal and lung infarction (tissue death)
  • Liver disease including hepatitis
  • Muscle damage 
  • Pancreatitis
  • Some cancers including melanoma
  • Cerebrovascular accident (CVA, stroke)
  • Drugs including anaesthetics, narcotics, methotrexate

With some chronic and progressive conditions, and some drugs, moderately elevated LD levels may persist.

Low levels of LD do not usually indicate a problem.

Is there anything else I should know?

Many things can affect LD results that are not necessarily a cause for concern. For example:

  • Strenuous exercise can cause temporary elevations in LD;
  • Damage to the sample during and after collection can cause falsely elevated results by causing breakage of red blood cells in the sample (haemolysis);
  • If your platelet count is increased, serum LD will be artificially high and not reflective of the LD actually present.

Common Questions

Is LD related to LDL cholesterol?

No, LDL cholesterol = low density lipoprotein cholesterol