Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1061 page)

   Diagnosis and monitoring of hypomagnesemia and hypermagnesemia, especially in renal failure or GI disorders

   To monitor preeclampsia patients being treated with magnesium sulfate, although in most cases, monitoring clinical signs (respiratory rate and deep tendon reflexes) is adequate, and blood magnesium levels are not required

   Interpretation

Increased In

   Iatrogenic (is usual cause; most often with impaired renal function).

   Diuretics (e.g., furosemide >80 mg/day, thiazides)

   Antacids or enemas containing Mg

   Laxative and cathartic abuse

   Parenteral nutrition

   Mg for eclampsia or premature labor

   Lithium carbonate intoxication

   Renal failure (when GFR approaches 30 mL/minutes); in chronic renal failure, hypermagnesemia is inversely related to residual renal function. Increase is rarely observed with normal renal function.

   Dehydration with diabetic coma before treatment

   Hypothyroidism