Evaluation of body magnesium stores

Muscle, erythrocyte, and bone magnesium was studied in patients with reduced, normal, and increased serum magnesium levels. Muscle magnesium content was shown to vary directly with muscle potassium levels and independently of other body magnesium stores. In contrast to the fact that serum magnesium did not consistently reflect muscle magnesium concentration there was a highly significant correlation between serum and bone magnesium levels. It would appear from these results that bone and extracellular fluid magnesium are the major magnesium pools in man increased during magnesium excess and decreased during magnesium depletion. Changes in muscle magnesium reflect changes in total body potassium and are not a valid indicator of total body magnesium.