Cholecalciferol (Vitamin D3)

Posted on October 7, 2009


Vitamin D3 has several forms:

  • Cholecalciferol, (sometimes called calciol) which is an inactive, unhydroxylated form of vitamin D3)
  • Calcidiol (also called 25-hydroxyvitamin D3), which is the form measured in the blood to assess vitamin D status
  • Calcitriol (also called 1,25-dihydroxyvitamin D3), which is the active form of D3.


7-Dehydrocholesterol is the precursor of vitamin D3 and forms cholecalciferol only after being exposed to solar UV radiation.

Cholecalciferol is then hydroxylated in the liver to become calcidiol (25-hydroxyvitamin D3).

Next, calcidiol is again hydroxylated, this time in the kidney, and becomes calcitriol (1,25-dihydroxyvitamin D3). Calcitriol is the most active hormone form of vitamin D3.