Lactate Dehydrogenase (LDH) Test

LDH stands for lactate dehydrogenase. It is a substance (enzyme) found in almost all tissues of your body, including the heart, liver, muscles, and blood cells. It helps your body produce energy.

Normally, only a small amount of LDH is present in the blood. But when cells are damaged or injured, LDH leaks into the bloodstream.

The LDH test is a simple blood test that measures the amount of this enzyme in your blood. Doctors may recommend this test to detect signs of tissue damage or to monitor certain health conditions. Higher-than-normal LDH levels can be a sign that something is affecting your body, such as an infection, injury, or disease, haemolysis/haemolytic anaemia, or cancer. However, this test alone does not identify the exact cause and is usually used with other tests.

Your doctor may suggest an LDH test if you have symptoms or conditions that could involve cell or tissue damage, especially involving the muscles, liver, lungs, kidneys, or red blood cells. 

You may need this test if you have symptoms such as: 

• Unexplained weakness
• Signs of infection or inflammation (such as fever, pain, redness)
• Symptoms of anaemia (like tiredness, pale skin, or shortness of breath)
• Liver-related symptoms (such as jaundice or abdominal pain)
• Muscle pain or injury

This test may also be advised in the following conditions or situations: 

• Suspected or existing heart problems (such as a heart attack) 
• Evaluation or monitoring of cancers (such as blood cancer)
• Tracking disease progression
• Checking how well the treatment is working.

The frequency of LDH testing depends on the individual’s health condition, symptoms, and treatment status, as outlined below: 

The LDH test does not diagnose a specific disease on its own, but it helps doctors identify if there is tissue damage in the body. It can support the diagnosis or monitoring of several conditions, such as:

• Infections (both bacterial and viral infections) can raise LDH levels
• Anaemia (where red blood cells break down)
• Liver diseases (such as hepatitis or liver damage)
• Muscle injury (due to trauma, intense exercise, or muscle disorders)
• Lung diseases (like pneumonia or other lung damage)
• Kidney disease (when there is damage to the kidney tissues)
• Heart conditions, including heart attack (in certain cases)
• Certain cancers (such as lymphoma, leukaemia, and others

What to Expect Before the LDH Test

No fasting is required for a standalone LDH test. You can eat and drink normally. However, if it is part of a broader package that includes fasting tests, your doctor may advise fasting for 8-12 hours. Avoid strenuous exercise for 24 hours before the test, as intense physical activity can temporarily raise LDH levels and affect interpretation. Always inform your doctor about any ongoing medications.

What to Expect During the Blood Collection

A phlebotomist cleans the skin with an antiseptic, then places an elastic band around your upper arm to make the veins easier to access. A small needle is inserted into the vein; you may feel a brief pinch. Blood is collected into a labelled tube in under a minute.

What to Expect After the LDH Test

A small cotton swab and bandage are placed over the site to stop any minor bleeding. You can return to normal activities immediately. Minor bruising is normal and disappears quickly. If dizzy, sit and rest for a few minutes.

The LDH test measures only one parameter:

• Levels of the LDH enzyme in the blood.

Lactate dehydrogenase (LDH) is an enzyme found inside the cytoplasm of cells throughout the body. It exists in five different forms (isoenzymes) and is most abundant in the heart, liver, skeletal muscles, kidneys, and red blood cells, with smaller amounts in the lungs, smooth muscles, and brain.

LDH plays an important role in energy production by helping convert lactate to pyruvate, especially when oxygen levels are low. Since LDH is normally present inside cells, it is released into the bloodstream when cells get damaged or break down. For this reason, LDH levels in the blood are often used as a general indicator of tissue or cell injury in the body.

The LDH normal range is given in the table below.

Note:

• Normal ranges may vary slightly depending on the laboratory and clinical context.
• Results should always be interpreted along with symptoms and other tests as needed.
• For the LDH test cost, please check our app/website.

The table below provides a general interpretation of LDH test results based on whether levels are high or low.

Note:

• Test results may vary depending on exercise intensity and certain medications.
• Always consult your doctor to understand your results properly.

The LDH blood test is a simple test. While it is generally safe, there are minimal risks and certain limitations to consider.

Risks (these are rare and usually resolve quickly on their own)

• You may feel slight pain or a prick when the needle is inserted.
• Mild bruising, swelling, or bleeding at the site may occur.

Limitations

• A high LDH level does not always mean you have a serious medical condition or need treatment.
• Levels can increase due to intense physical exercise or certain medications (such as aspirin).
• Results may be affected if red blood cells break during sample collection or handling (haemolysis), leading to falsely high values.
• LDH is a non-specific marker, meaning it cannot identify the exact cause or location of the problem on its own.

Since the LDH test is non-specific, doctors usually recommend other tests to find the exact cause of high levels, such as:

• LDH isoenzyme
• Complete blood count (CBC) with peripheral blood smear (PBS)
• Liver function tests
• Kidney function tests
• Troponin
• C-reactive protein (CRP) test

Pro Tip: For the most stress-free experience, book a LDH test on PharmEasy. Enjoy professional service and accurate results without stepping out of your house.