Lactate Dehydrogenase (LDH) Test

Lactate dehydrogenase (LDH) is an enzyme found in almost every cell of the body, where it plays a central role in energy production. When cells are damaged or destroyed, they release LDH into the bloodstream, so measuring the amount of LDH in a simple blood sample gives a useful indication of the degree of cell turnover or tissue injury occurring somewhere in the body. This test is used to investigate unexplained symptoms such as persistent fatigue, fever, jaundice, muscle pain or breathlessness, and it supports the monitoring of a wide range of conditions including haemolytic anaemias, liver disease, muscle disorders, certain cancers and tissue damage following injury or infarction. It is also frequently requested as part of a broader diagnostic workup when the underlying cause of illness is unclear.

What the test measures

• Lactate dehydrogenase (LDH): The total concentration of this enzyme in the blood, reported in units per litre (U/L). Because LDH is present in so many tissues, an elevated result is not specific to one organ, but it is a valuable signal that further targeted investigation is warranted. Your clinician will interpret the LDH level alongside your symptoms, medical history and other test results to identify the likely source of any abnormality.

Why it matters

LDH is a sensitive, widely available marker of cell damage and tissue turnover. A normal result can be reassuring when investigating unexplained symptoms, while a raised result helps direct further assessment towards the most likely underlying cause, whether that is blood, liver, muscle, heart or another tissue. Serial LDH measurements are also useful for tracking the progress of a known condition or response to treatment over time. Because the enzyme is not organ-specific, the result is always interpreted in context, and your doctor will discuss what it means for you and whether any additional tests are needed.

• Lactate dehydrogenase (LDH)

No special preparation required.

For blood tests, we recommend drinking plenty of water beforehand to ensure smooth sample collection. If you are taking any regular medication, continue to do so unless advised otherwise by your doctor.