Disorders of Magnesium: Physiology

Abstract

Magnesium (Mg²⁺) is the second most common intracellular cation next to K⁺ in the body. A 70 kg individual has approximately 25 g of Mg²⁺. About 67% of this Mg²⁺ is present in the bone, about 20% in the muscle, and 12% in other tissues such as the liver. Only 1–2% is present in the extracellular space. In plasma, Mg²⁺ exists as free (60%) and bound (40%) forms. About 10% is bound to HCO₃ ⁻, citrate, and phosphate and 30% to albumin. Only the free and nonprotein-bound Mg²⁺ is filtered at the glomerulus.