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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, including 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 have this test if your doctor 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 doctor 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 five separate 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 predominantly in heart tissue. LDH-5 is found mostly in the liver.

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

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

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 requires a blood sample, which is drawn through a needle from a vein in your arm.  

Does this test pose any risks?

Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.

What might affect my test results?

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

Anesthetics, aspirin, narcotics, and certain other drugs can raise your LDH. Drugs containing 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.  Certain medications may affect your results.  Be sure your doctor 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.