Vitamin D3 vs D2

Written by Sarah Chen, MS Nutrition Science, RDN

DJP

Reviewed by Dr. James Park, MD, Board Certified Internal Medicine

Published March 8, 2026

This content is for informational purposes only and does not constitute medical advice. Consult your healthcare provider before starting any supplement. Full disclaimer

TL;DR — Quick Answer

Vitamin D3 is superior to D2 for raising and maintaining serum 25(OH)D levels. D3 is 56-87% more effective at raising blood levels and maintains them longer. D2 is plant-derived and historically used in prescriptions, but D3 is now available in vegan forms from lichen.

Head-to-Head Comparison

Criteria	Vitamin D3	D2	Winner
Potency (Serum Level Increase)	High — 56-87% more effective at raising 25(OH)D	Lower — less efficient per IU	Vitamin D3
Duration of Effect	Long — maintains levels for weeks after dosing	Short — levels decline faster after discontinuation	Vitamin D3
Stability	More stable in storage and various conditions	Degrades faster with humidity, temperature, and time	Vitamin D3
Vegan Availability	Available — lichen-derived D3 is vegan	Inherently vegan — derived from fungi/yeast	Tie
Clinical Evidence for Health Outcomes	Strong — majority of positive trials used D3	Mixed — fewer trials, weaker outcome data	Vitamin D3

Detailed Analysis

Potency (Serum Level Increase)

Multiple studies confirm D3 produces a greater and more sustained increase in total serum 25(OH)D compared to equimolar doses of D2, due to stronger binding affinity to vitamin D-binding protein.

Duration of Effect

D3 has a longer half-life in circulation. After a single large dose, D3 maintains elevated serum levels for approximately 14 days longer than D2.

Stability

D2 is more sensitive to environmental conditions during storage, leading to faster degradation in supplements and fortified foods, which can reduce actual delivered dose.

Vegan Availability

D2 has traditionally been the vegan default since it comes from UV-irradiated fungi. However, lichen-derived D3 is now widely available, making both forms accessible to vegans.

Clinical Evidence for Health Outcomes

A meta-analysis found that D3 supplementation was associated with reduced all-cause mortality, while D2 was not. Most clinical trials demonstrating bone, immune, and cardiovascular benefits have used D3.

Our Verdict

Vitamin D3 is the clear winner for supplementation. It is significantly more potent at raising blood levels, maintains those levels longer, is more stable in supplement form, and has stronger associations with positive clinical outcomes. Unless you specifically need a prescription D2 formulation, choose D3 — vegan lichen-derived options are widely available.

Learn more about

Vitamin D3

Frequently Asked Questions

Why do doctors still prescribe vitamin D2?

Vitamin D2 (ergocalciferol) was the first form available as a pharmaceutical and remains the standard prescription form in many countries due to regulatory inertia. High-dose D2 (50,000 IU) is a common prescription for deficiency correction. However, many practitioners are now switching to D3 as OTC high-dose options have become available.

References

Tripkovic L, Lambert H, Hart K, et al. (2012). Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. American Journal of Clinical Nutrition. DOI PubMed
Heaney RP, Recker RR, Grote J, Horst RL, Armas LA (2011). Vitamin D3 is more potent than vitamin D2 in humans. Journal of Clinical Endocrinology & Metabolism. DOI PubMed