Laboratory tests for the assessment of magnesium status in humans.

The magnesium content of the adult human is approximately 24 g (1 mol), about half lies in bone and half in soft tissue. Less than 1% of the total body magnesium is present in blood, with approximately 0.3% present in serum. Total magnesium has been determined in several body tissues, but we lack information about free magnesium, which has physiologic significance. Current assessment of magnesium status is difficult as there is no simple, rapid and accurate test(s) to indicate total body magnesium status. I discuss 12 tests in three functional categories that have been used clinically or in research to assess magnesium status. Determining total magnesium in tissues and physiologic tests may provide important information. A test for the routine determination of free magnesium in serum should improve the assessment of magnesium status. A combination of available tests is recommended.