Absorption, Transport, Storage, and Excretion of Magnesium
About 40 to 60% of the magnesium consumed is absorbed, but absorption efficiency can rise to about 80% when intakes are low. Magnesium is absorbed in the small intestine by both passive and active absorption. The active vitamin D hormone 1,25 (OH) vitamin D enhances magnesium absorption to a limited extent. About half of the magnesium is found in bones and the rest is stored in other tissues , such as muscles. The kidneys primarily regulate blood concentration of magnesium and are able to reduce magnesium loss into the urine when blood magnesium is low