Bioavailability of US commercial magnesium preparations

Magnes Res. 2001 Dec;14(4):257-62.


Magnesium deficiency is seen with some frequency in the outpatient setting and requires oral repletion or maintenance therapy. The purpose of this study was to measure the bioavailability of four commercially-available preparations of magnesium, and to test the claim that organic salts are more easily absorbed. Bioavailability was measured as the increment of urinary maginesium excretion in normal volunteers given approximately 21 mEq/day of the test preparations. Results indicated relatively poor bioavailability of magnesium oxide (fractional absorption 4 per cent) but significantly higher and equivalent bioavailability of magnesium chloride, magnesium lactate and magnesium aspartate. We conclude that there is relatively poor bioavailability of magnesium oxide, but greater and equivalent bioavailability of magnesium chloride, lactate, and aspartate. Inorganic magnesium salts, depending on the preparation, may have bioavailability equivalent to organic magnesium salts.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aspartic Acid / pharmacokinetics
  • Biological Availability
  • Dietary Supplements*
  • Female
  • Humans
  • Magnesium Chloride / pharmacokinetics
  • Magnesium Compounds / pharmacokinetics*
  • Magnesium Oxide / pharmacokinetics
  • Male
  • Middle Aged
  • United States


  • Magnesium Compounds
  • Magnesium Chloride
  • Aspartic Acid
  • Magnesium Oxide