Figure 1.

Mg balance (arrows show most common sites of Mg depletion with aging), including daily amount of Mg intake and excretion. Total human body content of Mg is 24 to 29 g. In order to maintain Mg balance, a healthy person needs to consume around 5–7 mg/kg/day. Daily intestinal absorption varies from 25 to 60% of Mg intake. In the kidney, 80% of circulating Mg is filtered and about 60% is reabsorbed along the kidney tubule. This results in a net excretion of about 5 mmol/day. Fecal excretion is about 7.5 mmol/day. The intracellular compartment provides the most important Mg stores.