Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1062 page)

   Addison disease and after adrenalectomy

   Controlled DM in older patients

   Accidental ingestion of large amount of sea water

Decreased In

   Almost always GI or renal disturbance; chronic Mg deficiency produces hypocalcemia secondary to decreased production and effectiveness of PTH.

   GI disease

   Malabsorption (e.g., sprue, small bowel resection, biliary and intestinal fistulas, abdominal irradiation, celiac disease, and other causes of steatorrhea; familial Mg malabsorption)

   Abnormal loss of GI fluids (chronic ulcerative colitis, Crohn disease, villous adenoma, carcinoma of the colon, laxative abuse, prolonged aspiration of GI tract contents, vomiting)

   Renal disease: a level >2 mEq/day in urine during hypomagnesemia indicates excessive renal loss.

   Chronic GN

   Chronic pyelonephritis

   Renal tubular acidosis

   Diuretic phase of acute tubular necrosis

   Postobstructive diuresis