Lactate Dehydrogenase (LDH) Test

A lactate dehydrogenase (LDH) test usually measures the level of lactate dehydrogenase (LDH) in a sample of your blood. In certain cases, LDH levels are measured in samples of other body fluids. This includes testing fluid from the spine (cerebrospinal fluid), the belly (peritoneal fluid), and the chest (pleural fluid).

LDH is also called lactic acid dehydrogenase. It is an enzyme. An enzyme is a protein that speeds up certain chemical reactions in your body.

LDH helps your cells make energy. It is found in almost all the tissues in your body. The largest amounts of LDH are found in your muscles, liver, kidneys, and red blood cells.

If disease or injury damages tissues that have LDH, their cells release the enzyme into your bloodstream or other body fluids. It's normal to have some LDH in your blood and body fluids. But if your LDH levels are high, it may be a sign of certain diseases or injuries.

An LDH test alone can't show what is damaging your tissues or where the damage is located. So, an LDH test is usually done with other types of tests that can help diagnose the problem.

Why this test is done

Because LDH testing is used for so many conditions, it's best to ask your health care provider why you need an LDH test. In general, the test is ordered if other tests and/or your symptoms suggest you have tissue damage or disease.

If you have a disease that affects LDH levels, you may need an LDH test to learn more about your condition and to find out if your treatment is helping.

How to prepare

You don't need any special preparations for an LDH blood test. If your test uses other fluid samples, your provider will tell you how to prepare.

Sample type

Blood CSF

Other names for this test

LD test, lactic dehydrogenase, lactic acid dehydrogenase