Lactate Dehydrogenase (LDH) Isoenzymes Test

Why this test may be ordered

• You have symptoms that suggest you have some type of tissue damage.
• You had a total LDH test that showed you have higher than normal levels of LDH.
• You have a condition that affects LDH levels, and your provider wants to learn more about your condition or find out if your treatment is helping.

Preparation and collection

You don't need any special preparations for an LDH isoenzymes test.

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. This usually takes less than five minutes.

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

Understanding results

The meaning of your LDH isoenzyme test results depends on the reason you had the test, your symptoms, and the results of other tests you've had. Ask your provider to explain what your results say about your health.

• LDH-1 that's higher than LDH-2: May be a sign of a certain type of anemia. Limitation: An LDH isoenzymes test alone cannot diagnose what is causing the damage. Next step: Your provider will interpret this pattern along with your symptoms and other test results.
• LDH-5 that's higher than LDH-4: May be a sign of liver damage or disease. Limitation: An LDH isoenzymes test alone cannot diagnose what is causing the damage. Next step: Your provider will interpret this pattern along with your symptoms and other test results.
• High levels of two or more isoenzymes: High levels of two or more isoenzymes Limitation: High levels of two or more isoenzymes may mean you have two different conditions. Or it could be a sign of cancer that has spread to different tissues. Next step: Your provider will interpret this pattern along with your symptoms and other test results. Regular LDH isoenzyme testing may be done to see whether cancer is getting better during and/or after treatment.
• Low levels of LDH isoenzymes: May be affected by vitamin C or E intake or rarely a genetic disorder. Limitation: Lower than normal LDH isoenzyme levels are not common and usually are not considered to be a health problem. They may be affected by taking large amounts of vitamin C or vitamin E. There is also a rare genetic disorder that can cause low LDH levels. Next step: Talk with your provider if you have questions about your results.

• An LDH isoenzymes test alone cannot diagnose what is causing the damage.
• Because each LDH isoenzyme is found in more than one type of tissue, other more specific tests are often used with or instead of an LDH isoenzymes test to more accurately identify which tissue is damaged.
• High LDH isoenzyme levels do not always mean you have a medical condition that needs treatment; they can be caused by intense exercise, certain medicines (e.g., aspirin), or red blood cells breaking open during sample collection.
• Lower than normal LDH isoenzyme levels are not common and usually are not considered to be a health problem; they may be affected by taking large amounts of vitamin C or vitamin E, or rarely by a genetic disorder.

What to do next

The meaning of your LDH isoenzyme test results depends on the reason you had the test, your symptoms, and the results of other tests you've had. Ask your provider to explain what your results say about your health.

• Why do I need this test?
• What do my results mean about my health?
• Are there other tests I should have?

Evidence source

U.S. National Library of Medicine: Lactate Dehydrogenase (LDH) Isoenzymes Test