Lactate Dehydrogenase (LDH) Isoenzymes Test Test

This test measures the different forms of LDH in your blood to help find out which tissues may be damaged.

What this test measures

This test measures lactate dehydrogenase (LDH) isoenzymes in a sample of your blood. LDH is an enzyme found in almost all tissues, with five forms (isoenzymes) found in specific tissues: LDH-1 in heart and red blood cells, LDH-2 in white blood cells, LDH-3 in lungs, LDH-4 in kidneys and pancreas, and LDH-5 in liver and skeletal muscles.

What your results mean

Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.

Higher-than-normal results

A high level of one or more LDH isoenzymes usually means you have some type of tissue damage. The type of disease or damage depends on which isoenzymes are high and how they compare. For example, LDH-1 higher than LDH-2 may be a sign of a certain type of anemia, and LDH-5 higher than LDH-4 may be a sign of liver damage. High levels of two or more isoenzymes may mean two different conditions or cancer that has spread.

Lower-than-normal results

Lower than normal LDH isoenzyme levels aren't common and usually aren't considered to be a health problem. Levels may be affected by taking large amounts of vitamin C or vitamin E. A rare genetic disorder can also cause low LDH levels.

Frequently asked questions

What is an LDH isoenzymes test?

It measures the five forms of LDH enzyme in your blood to help find out which tissues may be damaged.

Why would I need this test?

It is used as a general test to check for tissue damage and to help show which organs may be damaged.

What conditions can cause high LDH isoenzymes?

Conditions include anemia, kidney disease, liver disease, pancreatitis, pulmonary embolism, muscular dystrophy, and some cancers.

Can high LDH isoenzymes be caused by something other than disease?

Yes, intense exercise, certain medicines like aspirin, or red blood cells breaking open during sample collection can cause high levels.

What do low LDH isoenzyme levels mean?

Low levels are not common and usually not a health problem. They may be affected by large amounts of vitamin C or E, or a rare genetic disorder.

Sources

MedlinePlus: Lactate Dehydrogenase (LDH) Isoenzymes Test — NIH MedlinePlus

Last updated July 7, 2026. Information is aggregated from official public sources and is not a substitute for professional medical care.