###1: Lactate dehydrogenase (LDH), catalytic concentration, serum or plasma

###5: What this test measures

###6: LDH helps convert lactate to pyruvate during energy production. Because the enzyme is present in the heart, liver, skeletal muscle, red blood cells, and other tissues, an abnormal level can reflect injury somewhere in the body.

###7: How the test is performed

###8: A blood sample is collected, and the serum or plasma is analyzed for LDH activity. The laboratory may use an enzymatic method, depending on the testing laboratory. You generally do not need to fast unless your clinician gives different instructions.

###9: Why clinicians order it

###10: LDH may be ordered as part of an evaluation for chest pain, suspected heart or liver injury, muscle symptoms, anemia, or other unexplained symptoms. It is often interpreted alongside tests such as CK, AST, ALT, and cardiac markers.

###11: Factors that can affect the result

###12: Strenuous exercise, muscle injury, injections, hemolysis during sample collection, and certain medicines can alter LDH activity. The sample should be handled carefully because breakdown of red blood cells in the tube can falsely raise the result.