The LDH test measures the amount of a special enzyme called lactate dehydrogenase in your blood. This enzyme helps your body turn sugar into energy for your cells. When tissues in your body—like your heart, liver, or muscles—are damaged, LDH is released into your blood. Doctors use this test to check for tissue damage, monitor certain diseases, and help find the cause of symptoms like unexplained pain or weakness. It is a helpful tool for understanding your overall health and for guiding further medical care.

What it Measures

The LDH test checks the level of lactate dehydrogenase, an enzyme found in almost every cell in your body. Here’s what it tells you:

Total LDH Level:
The test measures the total amount of LDH in your blood. High levels can signal that some of your body’s tissues have been damaged. This test does not tell you exactly where the damage is, but it shows that something may be wrong.
LDH Isoenzymes (if ordered):
Sometimes, doctors may order a more detailed test to look at different types of LDH, called isoenzymes. Each type is found mostly in certain organs:

LDH-1: Mainly in the heart and red blood cells.
LDH-2: Found in the white blood cells and the reticuloendothelial system (liver, spleen, lymph nodes).
LDH-3: Mostly in the lungs and other tissues.
LDH-4: Found in the kidneys, placenta, and pancreas.
LDH-5: Mainly in the liver and muscles.
This can help your doctor pinpoint which part of your body may be affected.

Why LDH Rises:
When your cells are injured—due to illness, injury, or disease—LDH leaks out and shows up in your blood. High LDH can be seen with liver problems, muscle injury, blood disorders, or even some cancers.
What Low LDH Means:
Low LDH levels are usually not a problem and rarely need further testing.
Other Body Fluids:
Sometimes, LDH is measured in fluids from other parts of your body (like spinal fluid or fluid around the lungs) to help find the cause of swelling or infection.

Why is it Important

Detects Tissue Damage:
The LDH test helps doctors find out if there is damage to your organs or tissues, such as your heart, liver, muscles, or blood cells. This is important for early diagnosis and treatment.
Monitors Disease Progress:
If you have a known condition like liver disease, kidney disease, or some cancers, this test helps doctors see if the disease is getting better or worse. It is often used to track recovery or response to treatment.
Guides Further Testing:
Abnormal results can alert your doctor to look for specific problems, such as infections, anemia, or muscle disorders. It helps guide what tests or treatments you may need next.
Assists in Emergency Situations:
In cases of sudden symptoms like chest pain, weakness, or unexplained fatigue, the LDH test can quickly show if there is tissue damage, helping doctors make fast decisions.
Checks for Complications:
The test is useful for checking complications in diseases like cancer, where LDH levels can rise if the disease spreads or worsens.

When Should I Get This Test?

You may need an LDH test if you:

Have symptoms like unexplained pain, swelling, or weakness.
Are being checked for liver or kidney disease.
Have been diagnosed with cancer and need to monitor its progress.
Have had a recent injury or surgery and your doctor wants to check for tissue damage.
Show signs of blood disorders, such as anemia or unusual bruising.

Interpretation of Test Results

Understanding what your results might mean is helpful, but always discuss them with a doctor for a proper diagnosis.

Result Type	What it Means
Normal	LDH levels are within the healthy range. No major tissue damage is detected.
Borderline	LDH is slightly higher or lower than normal. May be due to minor issues or temporary changes. Further tests may be needed.
Abnormal	LDH is much higher than normal. This can mean tissue damage from illness, injury, or disease. Your doctor will look for the cause.

(Note: Specific normal ranges can vary slightly between labs and depending on individual factors. Always refer to the ranges provided on your report and consult your doctor.)

Additional Information

The LDH test alone cannot tell exactly where the problem is; more tests may be needed for a clear diagnosis.
Some medicines or intense exercise can affect LDH levels. Always inform your doctor about any medications or recent activities.
If your results are abnormal, follow your doctor’s advice for further tests or treatment.

Test Requirements

Sample Type: Blood sample, usually taken from a vein in your arm.
Preparation Needed: Fasting is not required for this test.
Precautions: No special precautions are needed, but let your doctor know if you are taking any medicines or have had recent injuries.

FAQs

Do I need to fast before the LDH test?
No, fasting is not required for the LDH test. You can eat and drink as usual before your blood sample is taken. This makes the test easy and convenient for most people.
What does a high LDH result mean?
A high level usually means there is some tissue damage in your body. This could be due to an injury, infection, liver problem, or another health issue. Your doctor will use other tests and your symptoms to find out more.
Can pregnancy affect my test results?
Yes, LDH levels can sometimes be higher during pregnancy, especially if there are pregnancy-related complications. Always tell your doctor if you are pregnant so they can interpret your results correctly.
What should I do if my level is abnormal?
If your test result is not normal, don’t panic. Your doctor will review your health history, symptoms, and may order more tests to find the cause. Follow their advice for the next steps.
Is the test enough to diagnose a disease?
No, this test is just one part of your health check. It shows if there’s tissue damage but does not tell where or why. Your doctor will use other tests and your symptoms to make a diagnosis.

For more information, see Netmeds Health Library: Fatty Liver: Causes, Symptoms And Treatment

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