Cholecalciferol Alternative Names
Cholecalciferol is also known as vitamin D3. 1
Chemical and Biological Nomenclature
Vitamin D3 is the most common alternative name for cholecalciferol, distinguishing it from ergocalciferol (vitamin D2), which is the plant-derived form 1
The chemical name according to the International Union of Pure and Applied Chemistry is 9,10-secocholesta-5,7,10(19)-trien-3beta-ol 1
Cholecalciferol is technically classified as a steroid hormone or secosteroid rather than a true vitamin, since the human body can synthesize it endogenously through ultraviolet exposure of the skin 1
Metabolic Forms
Cholecalciferol is the endogenous precursor form that is derived from cholesterol in the skin upon UV exposure 1
Its hydroxylated derivative is called calcidiol or 25-hydroxyvitamin D3 [25(OH)D3], which has partial activity and is the form measured to diagnose deficiency 1
The fully active dihydroxy form is called calcitriol or 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], which is the biologically active hormone 1, 2, 3
Clinical Distinction from Vitamin D2
Cholecalciferol (D3) is more potent and has superior bioavailability compared to ergocalciferol (vitamin D2), maintaining serum levels for longer periods 4, 5, 6
Vitamin D3 is the preferred form for supplementation due to its longer duration of action and better efficacy at raising serum 25-hydroxyvitamin D levels 5, 6