review
Vitamin D3 vs D2: Which Form Is Best for Absorption & Bone Density?
Clinical comparison of Vitamin D3 (cholecalciferol) vs Vitamin D2 (ergocalciferol): why D3 is 87% more potent at raising sustained 25(OH)D blood levels.
By Nourish By Nutrients Editorial Team •
Updated: 2026-11-09
Key Evidence Takeaways:
- Vitamin D3 is identical to the cholecalciferol synthesized in human skin from sunlight, whereas D2 is derived from irradiated fungi/yeasts.
- Meta-analyses show Vitamin D3 is roughly 87% more potent at sustaining circulating serum 25(OH)D due to higher binding affinity to vitamin D-binding protein.
- D2 has a shorter half-life and degrades more rapidly when stored in multivitamin tablets.
- Vegan D3 sustainably extracted from wild lichen offers identical bioequivalence to traditional lanolin-derived D3.
Frequently Asked Questions
Why do doctors still prescribe 50,000 IU Vitamin D2?
High-dose 50,000 IU D2 capsules were historically the first FDA-approved prescription pharmaceutical form. However, modern clinical guidelines increasingly favor daily or weekly over-the-counter Vitamin D3 for superior sustained bioavailability.
Is Vitamin D3 vegan?
Most commercial D3 is extracted from sheep lanolin (wool grease). However, vegan Vitamin D3 sustainably harvested from wild lichen is 100% plant-based and molecularly identical.