* Dietary Supplement * Pharmaceutical Grade * Compare Active Ingredient To Blaine MagOx 400®† * 21st Century...For a Healthier Future MgO 400 mg (Magnesium Oxide) Necessary for the metabolism of calcium, vitamin C, phosphorus, sodium, and potassium. Magnesium is essential for nerve and muscle function , and for converting blood sugar to energy. Ninety percent of Americans don"t get enough magnesium in their diets. Certain prescription drugs such as loop and thiazide diuretics, cisplatin, cyclosporine and antibiotics may deplete magnesium.