Lactic Dehydrogenase Test (LDH) -Why am I having this test?

Lactic Dehydrogenase Test is done to help check for conditions that might cause tissue damage, such as infection, blood disease, or liver disease.

LDH testing can also be used to monitor the severity of an illness or the progress of therapy.

What is being tested?

This test checks the level of LDH in your blood. LDH is an enzyme that is found in the blood and in many tissues throughout the body, including your heart, liver, kidneys, muscles, brain, lungs, and red blood cells. LDH is made up of different parts called isoenzymes. Different LDH isoenzymes are found in different parts of the body. They are classified as follows:

• LDH-1. This isoenzyme is found in the heart.
• LDH-2. This isoenzyme is found in the red blood cells.
• LDH-3. This isoenzyme is found in the lungs and other tissues.
• LDH-4. This isoenzyme is found in the kidneys, placenta, and pancreas.
• LDH-5. This isoenzyme is found in the liver.

What kind of sample is taken?

A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel.

How do I prepare for this test?

• Do not exercise on the day of the test, or as directed by your health care provider.
• Follow your health care provider’s instructions about taking or not taking medicines before the test. Some medicines can affect the results of the test.

How are the results reported?

Your test results will be reported as values. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:

• LDH levels:
  • Adult or elderly: 100–190 units/L at 37°C or 100–190 units/L (SI units).
  • Child: 60–170 units/L at 30°C.
  • Infant: 100–250 units/L.
  • Newborn: 160–450 units/L.
• Isoenzymes, adult or elderly:
  • LDH-1: 17–27%.
  • LDH-2: 27–37%.
  • LDH-3: 18–25%.
  • LDH-4: 3–8%.
  • LDH-5: 0–5%.

What do the results mean?

Increased levels of LDH may indicate a number of health conditions, including:

• Heart attack.
• Lung disease.
• Liver disease.
• Kidney disease.
• Diseases that affect the formation of red blood cells, or indication of early destruction of red blood cells.
• Diseases and injuries that damage muscle tissues.
• Injury to the intestines due to poor blood supply (intestinal ischemia).
• Certain types of cancer.
• Inflammation or infection of the pancreas.
• Heat stroke.
• Shock.
• Severely low blood pressure (hypotension).
• Infection.
• Severe dehydration.

Several factors and conditions can affect the levels of LDH in your blood. Your health care provider will rule them out in order to make an accurate diagnosis. He or she will consider whether you:

• Had strenuous exercise just before the test.
• Take medicines or substances that can increase or decrease LDH levels.

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Ask your health care provider, or the department that is doing the test:

• When will my results be ready?
• How will I get my results?
• What are my treatment options?
• What other tests do I need?
• What are my next steps?

Summary

• This test checks the level of lactic dehydrogenase (LDH) in your blood. LDH is an enzyme that is found in the blood and in many tissues throughout your body, including your heart, liver, kidneys, muscles, brain, lungs, and red blood cells.
• LDH testing is done to help check for conditions that might cause tissue damage, such as infection, blood disease, or liver disease. It can also be used to monitor the severity of an illness or the progress of therapy.
• Higher-than-normal levels of LDH may indicate various health conditions. Talk with your health care provider about what your results mean.