GO:0036378:   calcitriol biosynthetic process from calciol
Conversion of vitamin D3 from its largely inactive form (calciol, also called cholecalciferol) into a hormonally active form (calcitriol). Conversion requires 25-hydroxylation of calciol in the liver to form calcidiol, and subsequent 1,alpha-hydroxylation of calcidiol in the kidney to form calcitriol.