Vitamin D2 vs D3: What's the Difference?
Last updated: August 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy
D3 is the better choice. Both raise vitamin D levels, but D3 does it more efficiently and holds levels longer — a meta-analysis found D3 roughly twice as effective as D2 at raising serum 25(OH)D. Vegan D3 from lichen now exists, so D2 is no longer the only plant-based option.
Key takeaways
- D3 raises and maintains blood levels more effectively per unit dose.
- D2 comes from fungi and UV-exposed mushrooms; D3 from lanolin or lichen.
- Take either with a fat-containing meal — absorption is meaningfully better.
Why D3 wins
D2 (ergocalciferol) and D3 (cholecalciferol) both convert to 25-hydroxyvitamin D and both bind the vitamin D receptor. The difference is pharmacokinetic: D2 has lower affinity for vitamin D binding protein and is cleared faster, so the same dose produces a smaller and shorter-lived rise. A systematic review found D3 substantially more effective at raising and maintaining serum levels.
Where D2 still appears
It is the traditional vegan option and the form in some high-dose prescription regimens, often given weekly. UV-exposed mushrooms are the main food source. If you are using D2, larger or more frequent doses compensate for the lower efficiency.
The practical points that matter more
Take it with a meal containing fat — absorption improves substantially. Get a 25(OH)D blood test rather than guessing, because it tells you whether you need a maintenance dose, a correction course or nothing at all. And above roughly 37 degrees latitude, skin synthesis is negligible from October to March, which is why winter supplementation is widely recommended.
Key ingredients to understand
The ingredients most relevant to this question, with what the evidence actually supports:
- Vitamin D3 (Cholecalciferol) — Vitamin D3 is the form your skin makes from sunlight and the form that raises and maintains blood levels most effectively. Deficiency is…
- Vitamin D2 (Ergocalciferol) — Vitamin D2 comes from plant and fungal sources and is the standard vegan option. It does raise vitamin D levels, but less effectively than D3…
- Vitamin D — Vitamin D is essential for bones and plays a role in immunity. Deficiency is common, and supplementing clearly helps if you are low — but large…
- Vitamin K2 — Vitamin K2 is a fat-soluble vitamin that helps the body direct calcium toward bone and away from artery walls. The clearest research is on…
Frequently asked questions
Is vegan D3 available?
Yes, from lichen. It is the better vegan option now, since it has D3's efficiency without an animal source.
How much should I take?
400–1,000 IU daily is typical maintenance guidance. Correcting a confirmed deficiency uses more, under supervision. The upper limit is 4,000 IU.
Can you take too much?
Yes. Sustained very high intake causes hypercalcaemia — nausea, weakness, kidney problems. It requires a lot, but it happens.
Related on FactoWiki
- All health answers
- Ingredient evidence guides
- Vitamin D3 (Cholecalciferol) — ingredient guide
- Vitamin D2 (Ergocalciferol) — ingredient guide
- How we review
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