The Lactate Dehydrogenase (LDH) blood test measures the level of lactate dehydrogenase, an enzyme found in various tissues. Elevated levels in the bloodstream indicate that cells have been damaged or destroyed. The LDH test suggests injury or disease, but it does not pinpoint the exact location or cause. Therefore, medical professionals typically use LDH test results in conjunction with other clinical information and diagnostic tests to form a complete picture of a patient’s health.
The LDH Enzyme
Lactate dehydrogenase (LDH) is an enzyme present in nearly all living cells, playing a significant role in the body’s energy production. Its primary function involves the reversible conversion of pyruvate to lactate, a process essential for cellular respiration. This reaction allows cells to continue generating energy, particularly when oxygen levels are low.
LDH is widely distributed throughout the body, with high concentrations found in organs such as the heart, liver, kidneys, muscles, red blood cells, brain, and lungs. When cells in these tissues are damaged due to injury, disease, or infection, they release their contents, including LDH, into the bloodstream. The presence of elevated LDH in the blood therefore serves as a general indicator of cellular damage.
Reasons for an LDH Test
Medical professionals order an LDH blood test for several reasons, primarily to detect and monitor tissue damage or disease. It can help determine if there has been cellular injury in various parts of the body, such as the heart, liver, kidneys, or muscles.
The test is also used to monitor the progression of certain medical conditions, including some cancers, muscle disorders, and anemias. Additionally, an LDH test can help assess the severity of specific injuries or infections by indicating the extent of cellular destruction.
The LDH Test Procedure
Undergoing an LDH blood test is a straightforward process, similar to any routine blood draw. A healthcare professional typically collects a blood sample from a vein, most commonly in the arm. Before the draw, the skin is cleaned with an antiseptic. A small needle is then inserted into the vein to collect a blood sample. The procedure usually takes only a few minutes. Generally, no special preparation, such as fasting, is required for an LDH blood test.
Interpreting LDH Results
Interpreting LDH results involves considering various factors, as elevated levels generally suggest cellular or tissue damage. High LDH levels can be indicative of numerous conditions, including heart attack, liver disease (such as hepatitis or cirrhosis), kidney disease, lung disease, and certain types of anemia, particularly hemolytic anemia where red blood cells are destroyed, and megaloblastic anemia.
Muscle injuries, muscular dystrophy, bone fractures, pancreatitis, and severe infections like meningitis, mononucleosis, or HIV may cause increased LDH. Some cancers, including lymphoma, leukemia, testicular cancer, and metastatic melanoma, are also associated with higher LDH levels, which can sometimes reflect disease aggressiveness or treatment response.
It is important to understand that LDH is a non-specific marker; elevated levels do not pinpoint a single disease or the exact location of damage. Therefore, medical professionals always interpret LDH results in conjunction with a patient’s symptoms, medical history, and other diagnostic tests to determine the underlying cause.
Low LDH levels are uncommon and typically do not indicate a significant health problem. If LDH levels are abnormal, further evaluation is usually necessary to establish a precise diagnosis.