Lactate dehydrogenase (LDH) is an enzyme found in nearly all cells of the body, playing a fundamental role in cellular energy production. This enzyme facilitates the conversion of lactate to pyruvate, a molecule that can then be used to generate energy, especially when oxygen levels are low. LDH is present in various tissues, including skeletal muscles, heart, kidneys, liver, and red blood cells. A blood test measures the amount of LDH circulating in the bloodstream, providing insight into cellular activity and potential tissue damage.
Understanding Low LDH Test Results
Discovering a low lactate dehydrogenase level in a blood test is an uncommon occurrence. Unlike elevated LDH levels, which often signal tissue damage or disease, a low LDH result is typically not considered a significant clinical indicator on its own. It rarely points to an underlying health problem.
Laboratory reference ranges for LDH can vary slightly depending on the specific testing facility and the methods used. For adults, typical normal ranges generally fall between 140 to 280 units per liter (U/L), though these values can differ. Interpreting a low result requires consideration of the specific laboratory’s established normal range.
Potential Causes of Low Lactate Dehydrogenase
Low lactate dehydrogenase levels can stem from two primary categories: rare genetic conditions or external factors that interfere with laboratory testing. One cause is a genetic LDH deficiency, an inherited disorder that affects the body’s ability to produce functional LDH enzymes. This deficiency can manifest in two main forms, LDH-A deficiency and LDH-B deficiency, each impacting different parts of the body.
LDH-A deficiency, also known as Glycogen Storage Disease Type XI, primarily affects skeletal muscles. Individuals with this condition may experience impaired energy metabolism in their muscles, particularly during strenuous activity. In contrast, LDH-B deficiency, while rarer, mainly impacts the heart muscle but often presents without noticeable symptoms.
Beyond genetic factors, certain external influences can lead to a falsely low LDH reading on a lab test. An extremely high intake of ascorbic acid, commonly known as Vitamin C, is a well-documented example. High doses of Vitamin C can interfere with the chemical reactions used in the laboratory assay to measure LDH, leading to an artificially reduced result. Similarly, very high levels of Vitamin E have also been observed to interfere with the LDH assay, producing a misleadingly low reading.
Associated Symptoms and Conditions
The presence or absence of symptoms associated with low lactate dehydrogenase levels largely depends on the underlying cause. When a low LDH reading is due to genetic LDH-A deficiency, individuals may experience specific muscle-related symptoms. These can include muscle fatigue, pain, and cramping, especially after engaging in vigorous physical exercise. In more severe instances, rhabdomyolysis, a condition involving the breakdown of muscle tissue, can occur, leading to muscle weakness and dark urine.
Conversely, if a low LDH result is caused by interference from substances like high doses of Vitamin C or Vitamin E, there are typically no associated symptoms. Genetic LDH-B deficiency is also generally asymptomatic.
When to Consult a Doctor
Any abnormal laboratory result, including a low lactate dehydrogenase level, warrants a discussion with a healthcare provider for proper interpretation. A doctor will evaluate the low LDH result within the broader context of a patient’s overall health status, existing symptoms, and other blood test findings. This comprehensive approach helps determine if the low reading holds any clinical significance.
If a genetic deficiency is suspected due to corresponding symptoms, particularly muscle-related issues, the doctor may recommend further diagnostic tests. These could include a creatine kinase (CK) test, which measures another enzyme released when muscles are damaged, or specific genetic testing to confirm an LDH enzyme deficiency. If vitamin interference is considered a possibility, the healthcare provider might advise temporarily pausing the intake of high-dose Vitamin C or Vitamin E supplements. Subsequently, a repeat LDH test can be performed to see if the enzyme levels return to the normal range, confirming the interference as the cause.