Magnesium deficiency is cause by-

Excessive losses INADEQUATE INTAKE Starvation Malnutrition (esp. alcoholism) Parenteral alimentation GI- Prolonged vomiting/nasogastric aspiration Chronic diarrhoea/laxative abuse Malabsorption Small bowel bypass surgery Fistulae URINARY- Diuretic therapy (loop, thiazide) Alcohol Tubulotoxic drugs (gentamicin, cisplatin) Volume expansion (e.g. primary hyperaldosteronism) Diabetic ketoacidosis Post-obstructive diuresis Recovery from acute tubular necrosis Inherited tubular transpo defect (Bater's syndrome, Gitelman's syndrome Primary renal magnesium wasting) MISCELLANEOUS-Acute pancreatitis Foscarnet therapy Proton pump inhibitor therapy (prolonged) Hungry bone syndrome Diabetes mellitus. DAVIDSONS PRINCIPLES OF PRACTICAL MEDICINE 22ND EDITION PAGE NO-448