Lactate Dehydrogenase (LDH) Isoenzymes Test
This test measures lactate dehydrogenase (LDH) isoenzymes in a sample of your blood.
This test measures lactate dehydrogenase (LDH) isoenzymes in a sample of your blood. It's a general test that can help find out if you have tissue damage from disease or injury. It can also help show which organs and other tissues are likely to be damaged. But an LDH isoenzymes test alone cannot diagnose what's causing the damage. 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. The LDH enzyme helps your cells make energy. LDH 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. There are five forms of the LDH enzyme which are called LDH isoenzymes. Each isoenzyme has a slightly different structure and is found in specific tissues in your body: LDH-1 is mainly in your heart and red blood cells. LDH-2 is mainly in your white blood cells. It is also found in your heart and red blood cells, but in smaller amounts than LDH-1. LDH-3 is mainly in your lungs. Smaller amounts are found in other tissues. LDH-4 is mainly in your kidneys and pancreas. If you're pregnant, it's also found in the placenta (the organ that brings oxygen and nutrients to the baby). LDH-5 is mainly in your liver and skeletal muscles (muscles that attach to your bones to help you move). It's normal to have some LDH in your blood. But if disease or injury damages tissues that contain LDH, the cells release LDH isoenzymes into your bloodstream and your LDH levels will rise above normal. There are two ways to measure LDH: A total LDH test measures the total amount of LDH in your blood or other body fluids. It can't tell the difference between the types of LDH isoenzymes. So, this test can show possible tissue damage, but it can't show which tissue may be damaged. An LDH isoenzyme test measures the amount of each type of isoenzyme in your blood. This information helps your health care provider figure out which tissues may be damaged. 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. These tests can more accurately identify which tissue is damaged and the condition causing the damage. Other names: LD isoenzymes, lactic dehydrogenase isoenzyme, LDH fractionation
Why is this test ordered? An LDH isoenzyme testing may be used for many conditions, so it's best to ask your provider why you need this test. In general, the test is ordered if you: Have symptoms that suggest you have some type of tissue damage Had a total LDH test that showed you have higher than normal levels of LDH Have a condition that affects LDH levels, and your provider wants to: Learn more about your condition Find out if your treatment is helping
Clinical Interpretation
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. In general, 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 LDH isoenzymes are high and how your isoenzyme levels compare with each other. For example: LDH-1 that's higher than LDH-2 may be a sign of a certain type of anemia. LDH-5 that's higher than LDH-4 may be a sign of liver damage or disease. 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 LDH isoenzyme levels don't always mean you have a medical condition that needs treatment. High levels of certain LDH isoenzymes can be caused by intense exercise and certain medicines, including aspirin. It's also possible to have high LDH isoenzymes if many red blood cells broke open when your sample was collected and tested. Lower than normal LDH isoenzyme levels aren't common and usually aren't 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 with your provider. Learn more about laboratory tests, reference ranges, and understanding results .
Clinical Protocol & Patient Advice
- 1
You don't need any special preparations for an LDH isoenzymes test.
Usage Guidance
- Reference ranges vary by laboratory. Always discuss your specific results with a qualified healthcare professional.
Source: MedlinePlus, National Library of Medicine. View the original.