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Lactic Acid Dehydrogenase (Blood)

Does this test have other names?

Lactic dehydrogenase, LDH, lactate dehydrogenase

What is this test?

This is a blood test that measures the level of lactic dehydrogenase (LDH) in your body. LDH is an enzyme, or catalyst, found in many different tissues in your body. These include your red blood cells, skeletal muscles, kidneys, brain, and lungs. When your LDH rises, it means that tissues may have been damaged or are diseased.

Why do I need this test?

You may need this test if your healthcare provider suspects you have had a heart attack or may have tissue damage or disease. If you've already been diagnosed with a specific disease, you may have this test so your provider can watch your condition and see whether your treatment is working. 

What other tests might I have along with this test?

You may also have a lactate dehydrogenase isoenzyme test. Your total LDH is made up of 5 isoenzymes numbered LDH-1 through LDH-5. The concentration of each isoenzyme depends on the tissue. For example, LDH-1 and LDH-2 are found mainly in heart tissue. LDH-5 is found mostly in the liver.

A higher than normal total LDH means possible tissue damage. Your healthcare provider might order a lactate dehydrogenase isoenzyme test to find out which tissue is damaged or diseased. 

What do my test results mean?

Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. 

The normal range for total LDH is:

  • Newborn: 160 to 450 units per liter (units/L)

  • Infant: 100 to 250 units/L

  • Child: 60 to 170 units/L at 30° C

  • Adult/elderly adult: 100 to 190 units/L at 37° C

If your total LDH is higher than normal, it could mean that you have organ or tissue damage. But total LDH doesn't tell which tissue or organ may be damaged. If all of your LDH isoenzymes are higher than normal, you could have damage to several organs, including your heart, lungs, kidneys, and liver. Autoimmune diseases like lupus and advanced cancers can also cause higher LDH levels.

How is this test done?

The test is done with a blood sample. A needle is used to draw blood from a vein in your arm or hand. 

Does this test pose any risks?

Having a blood test with a needle carries some risks. These include bleeding, infection, bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may feel a slight sting or pain. Afterward, the site may be sore. 

What might affect my test results?

If the blood sample is contaminated or your red blood cells are broken, your LDH will be higher.

Anesthetics, aspirin, narcotics, and certain other medicines can raise your LDH. Medicines with ascorbic acid (vitamin C) can decrease your LDH levels. Alcohol also can affect your LDH levels.

How do I get ready for this test?

You don't need to prepare for this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use. 

Medical Reviewers:

  • Fraser, Marianne, MSN, RN
  • Haldeman-Englert, Chad, MD