What are the forms of calcium in plasma?

Updated: Dec 03, 2020
  • Author: Mahendra Agraharkar, MD, MBBS, FACP, FASN; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Plasma calcium is maintained despite its large movements across the gut, bone, kidney, and cells. Changes in calcium ions usually are accompanied by changes in total calcium in the ECF. In plasma, calcium exists in 3 different forms: (1) 50% as ionized or the biologically active form, (2) 45% bound to plasma proteins (mainly albumin), and (3) 5% complexed to phosphate and citrate. Because the proportion of bound calcium varies little within individuals, in the absence of severe acidosis or alkalosis, the amount of albumin is the major factor determining the amount of calcium that is bound.

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