Thursday, January 9 (2020); Body fluids and electrolytes
First of all, let us address the misnomer of "ionised" calcium. It's all ionised, people. Unless it is in a covalent bond with something, it is present as an ion. To be sure, it might be clinging to the side of an albumin molecule, or it might be complexed with a chelator like citrate, but it is still an ion, and not a member of a molecule per se. However, the trend of calling unbound calcium "ionised calcium" persists, and is prevalent at all levels of academic medicine. It is only this fraction which actually does anything useful, and is also the fraction which enjoys tight regulation by PTH and vitamin D; whereas the bound fraction is physiologically useless.