Physiology Gastrointestinal System 4fabc0a1 Calcium is absorbed from: A Duodenum B Jejunum C Ileum D Colon High-Yield Explanation All the divalent cations, except Mg++ , are absorbed from duodenum. Mg++ is absorbed from ileum. Calcium is absorbed mainly in duodenum and upper jejunum, not whole of jejunum.