Calcidiol is a hydroxycalciol that is calciol in which the hydrogen at position 25 has been replaced by a hydroxy group. A prehormone resulting from the oxidation of calciol in the liver, it is further hydroxylated in the kidney to give calcitriol, the active form of vitamin D3. It has a role as a metabolite, a bone density conservation agent, a nutraceutical, a mouse metabolite and a human metabolite. It is a diol, a hydroxycalciol and a member of D3 vitamins.