Lactate Dehydrogenase (LDH) is an enzyme found in nearly all body tissues, playing a role in cellular energy production. The LDH test measures its levels in the blood. This measurement provides general clues about overall health, particularly indicating if tissue damage or disease is present somewhere in the body. Elevated LDH serves as a broad indicator that prompts further investigation into a person’s health status.
What is LDH and How is it Measured?
Lactate Dehydrogenase is an enzyme that helps cells produce energy. It is found in many different tissues throughout the body, including the heart, liver, kidneys, muscles, brain, and blood cells. When cells are injured or die, they release LDH into the bloodstream.
The LDH test is a simple blood test, typically performed by drawing a sample from a vein in the arm. This test measures the total amount of LDH released into the bloodstream. Doctors may order this test as part of a diagnostic evaluation or to monitor certain health conditions, as elevated levels can signal cellular injury or disease.
Understanding Your LDH Levels
Normal LDH levels can vary slightly between laboratories, but for adults, a typical range is 140 to 280 units per liter (U/L). Infants and young children generally have higher normal LDH levels; for example, newborns may range from 135 to 750 U/L, and children up to 12 months from 180 to 435 U/L.
Higher-than-normal LDH levels indicate tissue damage, injury, or disease, as affected cells release LDH into the bloodstream. The severity of elevation can suggest the extent of tissue damage. Low LDH levels are less common and typically not a concern, though they can be linked to rare genetic conditions or high vitamin C intake.
LDH is a non-specific marker, meaning an elevated level indicates damage but does not pinpoint the exact location or cause. Healthcare providers use LDH results in conjunction with other tests, symptoms, and medical history for accurate diagnosis. For instance, while LDH can indicate tissue damage, other markers like troponin are more specific for heart injury.
Health Conditions Linked to LDH
Elevated LDH levels can occur in a variety of medical conditions when cells are damaged or destroyed.
Organ Damage
Heart conditions, such as a heart attack, can cause LDH levels to rise, typically increasing 12 to 24 hours after the event and peaking at 48 to 72 hours.
Liver diseases, including hepatitis and cirrhosis, commonly lead to increased LDH due to damage to liver cells.
Kidney injuries or disease can also result in elevated LDH levels.
In the lungs, conditions such as pulmonary embolism or pneumonia may cause an increase in LDH.
Blood Disorders and Infections
Blood disorders, including hemolytic anemia, where red blood cells are prematurely destroyed, and megaloblastic anemia, are frequently associated with higher LDH levels.
Muscle injuries from trauma, muscular dystrophy, or strenuous exercise can cause a temporary rise in LDH.
Severe infections, such as sepsis, meningitis, or encephalitis, often lead to elevated LDH.
Cancer
Various types of cancer, including lymphomas, leukemias, and certain solid tumors, can increase LDH levels. In cancer, elevated LDH is often associated with rapid tumor growth and can be used to monitor treatment response.
Factors Affecting LDH Test Results
Several factors unrelated to disease can influence LDH levels, which is important when interpreting test results.
Lifestyle and Medications
Strenuous physical activity, such as intense exercise, can temporarily elevate LDH levels.
Certain medications, including aspirin, anesthetics, narcotics, and procainamide, may lead to falsely increased LDH levels.
High concentrations of vitamin C might cause a falsely low LDH result.
Alcohol consumption can also affect LDH levels.
Sample Handling and Other Conditions
Hemolysis, the breakdown of red blood cells during blood draw or transportation, is a common cause of falsely elevated LDH because red blood cells contain high amounts of LDH, and their rupture releases the enzyme into the sample.
Pregnancy can lead to slightly altered LDH levels, particularly in the third trimester.
Elevated LDH during pregnancy might also indicate conditions like preeclampsia.
Individuals should inform their doctor about recent activities, medications, and any other relevant factors before undergoing the test for accurate interpretation.