The lactate dehydrogenase (LDH) isoenzyme test is a valuable diagnostic tool for evaluating tissue damage in the body. By measuring different types of LDH isoenzymes, this test helps identify affected organs and monitor the evolution of various medical conditions, offering crucial insight into a patient's health.
This test measures lactate dehydrogenase (LDH) isoenzymes in a sample of your blood. It is a general test that can help determine if you have tissue damage due to illness or injury. It can also help show which organs and other tissues are likely to be damaged. But an LDH isoenzyme test alone cannot diagnose the cause of the damage.
LDH is also called lactate dehydrogenase. It's an enzyme. An enzyme is a protein that speeds up certain chemical reactions in your body. The LDH enzyme helps your cells produce energy. LDH is found in nearly every tissue in your body. The largest amounts of LDH are found in your muscles, liver, kidneys, and red blood cells.
There are five forms of the LDH enzyme that are called LDH isoenzymes. Each isoenzyme has a slightly different structure and is found in specific tissues in your body:
It's normal to have a small amount of LDH in your blood. But if an illness or injury damages tissue that contains LDH, the cells release LDH isoenzymes into your bloodstream and your LDH levels will rise above normal.
There are two ways to measure LDH:
Because each LDH isoenzyme is found in more than one type of tissue, other, more specific tests are often used with or in place of an LDH isoenzyme test. These tests can more accurately identify what tissue is damaged and the condition causing the damage.
Other names: LD isoenzymes, lactate dehydrogenase isoenzyme, LDH fractionation
An LDH isoenzyme test is primarily used as a general test to check for tissue damage. It can also help determine the severity of the damage. An LDH isoenzyme test may be used to show which organs and other tissues are likely to be damaged, but other, more specific tests may be used instead.
An LDH isoenzyme test can be used with other tests to help diagnose and monitor many types of acute (sudden) and chronic (long-lasting) conditions. Conditions that can cause high LDH levels include:
LDH isoenzyme tests can also be used to determine if treatment for many conditions is working.
The test is used to learn how serious certain types of cancer can be and whether the cancer is likely to respond to certain treatments. Regular LDH isoenzyme tests may be done to see if the cancer improves during and/or after treatment.
An LDH isoenzyme test can be used for many conditions, so it's best to ask your provider why you need this test. In general, the test is required if you:
A health 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 in a test tube or vial. You may feel a slight prick when the needle goes in or out. This usually takes less than five minutes.
You do not need special preparations for an LDH isoenzyme test.
There are very few risks in taking a blood test. You may feel a slight pain or bruise where the needle was inserted, but most symptoms go away quickly.
What your LDH isoenzyme test results mean depends on why you took the test, your symptoms, and the results of other tests you took. Ask your provider to explain what your results say about your health.
In general, a high level of one or more LDH isoenzymes It usually means that you have some type of tissue damage. The type of disease or damage depends on which LDH isoenzymes are high and how your isoenzyme levels compare to one another. For example:
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.
Higher than normal levels of LDH isoenzymes don't always mean you have a medical condition that requires treatment. High levels of some LDH isoenzymes can be caused by strenuous exercise and certain medications, including aspirin. It is also possible to have high LDH isoenzymes if a lot of red blood cells exploded when your sample was taken and tested.
Lower-than-normal levels of LDH isoenzymes are not common and are not generally considered to be a health problem. Your levels of certain isoenzymes 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.
If you have questions about your results, talk to your provider.
Learn more about lab tests, reference ranges, and understanding results.