The health care provider draws blood from a vein or from a heel, finger, toe, or earlobe. The laboratory quickly spins (centrifuges) the blood to separate the serum (liquid portion) from the cells. The LDH test is done on the serum.

Your health care provider may ask you to stop taking drugs that may affect the test. Drugs that can increase LDH measurements include anesthetics, aspirin, clofibrate, fluorides, mithramycin, narcotics, and procainamide.

LDH is most often measured to check for tissue damage. The enzyme LDH is in many body tissues, especially the heart, liver, kidney, skeletal muscle, brain, blood cells, and lungs.

LDH affects the chemical reaction for the conversion of pyruvate and lactate . Exercising muscles convert (and red blood cells metabolize ) glucose to lactate. Lactate is released into the blood and is later taken up by the liver. The liver converts lactate back to glucose and releases glucose into the blood. Resting muscles, red blood cells, and other tissues then take up this glucose.

Normal values may vary slightly from one lab to another. A typical range is 105 - 333 IU/L (international units per liter).

Higher-than-normal levels may indicate:

• Cerebrovascular accident (CVA, stroke)
• Heart attack
• Hemolytic anemia
• Low blood pressure
• Infectious mononucleosis
• Blood deficiency (intestinal ischemia)
• Liver disease (for example, hepatitis )
• Muscle injury
• Muscular dystrophy
• New abnormal tissue formation (neoplastic) states
• Pancreatitis
• Tissue death (pulmonary infarction)

If the LDH level is raised, your doctor may order an LDH isoenzymes measurement.

Other conditions under which the test may be done:

• Anemia of vitamin B-12 deficiency
• Megaloblastic anemia
• Pernicious anemia

Abeloff MD, Armitage JO, Niederhuber JE, Kastan MB, McKenna WG. Clinical Oncology. 3rd ed. Philadelphia, Pa: Churchill Livingstone, 2004.

Ferri FF. Ferri's Clinical Advisor 2007. Philadelphia, Pa: Mosby, 2006.