Magnesium and phosphorus: the neglected electrolytes.

Magnesium and phosphorus normally are present in very low serum concentrations and usually are not included in common serum electrolyte laboratory studies. Though their normal serum concentrations are relatively low, both of these ionized minerals are necessary for many critical physiologic functions, and decreases in normal serum levels can have serious deleterious effects. Some of these effects, especially in myocardial tissues, may lead to permanent tissue damage. Hospitalized patients at greatest risk for developing hypomagnesemia or hypophosphatemia are trauma victims; individuals with poorly controlled diabetes mellitus, renal impairment, parathyroid dysfunction, or chronic alcoholism; and individuals who have been treated with antineoplastic agents.