GO:0036378

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. [GOC:BHF, GOC:rl, PMID:17426122, PMID:20511049]