Vitamin D versus D3, and what a label is telling you
Vitamin D is the family name. D2 and D3 are the two forms sold, both counted in the same units, and D3 raises blood 25(OH)D more per microgram. What the label words mean and when the difference is worth paying for.
What people ask us next.
- Is vitamin D the same as vitamin D3?
- Not quite. Vitamin D is the family name for a group of fat-soluble secosteroids, and D3 (cholecalciferol) is one of the two members sold, the other being D2 (ergocalciferol). A label reading only vitamin D does not say which one is inside, so the parenthetical on the Supplement Facts panel is the informative part. Both are counted in the same units, both raise serum 25-hydroxyvitamin D, and both count toward the same RDA, but they are not the same molecule.
- Is D3 better than D2?
- At raising blood levels, yes. A systematic review and meta-analysis found D3 more efficacious than D2 at increasing serum 25-hydroxyvitamin D (Tripkovic et al. 2012), and a 12-week randomised, double-blind, placebo-controlled trial in 335 women taking 15 mcg a day found the D3 groups gained roughly 15 to 16 nmol/L more in total 25(OH)D than the D2 group (Tripkovic et al. 2017). Both forms work; D3 simply gets more out of the same labelled dose.
- How do I tell which form a supplement contains?
- Read the parenthesis on the Supplement Facts panel. Cholecalciferol is vitamin D3. Ergocalciferol is vitamin D2. Marketing text on the front of the bottle is often just vitamin D, which is not specific enough. If the label lists lichen or lichen extract as the source, that is vegan-suitable D3; conventional D3 is derived from lanolin in sheep wool, and D2 is made by ultraviolet irradiation of yeast or fungi.
- Does a blood test tell the difference between D2 and D3?
- A standard test reports total 25-hydroxyvitamin D, which combines the D2-derived and D3-derived fractions, so it does not separate them unless the assay is specifically asked to. That is the point of the shared pathway: whichever form is taken, the liver converts it to the same measured storage form. This is also why both forms count toward the same intake targets and why an adequacy threshold of 50 nmol/L is not form-specific.
- Is vegan vitamin D always D2?
- No, not any more. Vitamin D2 from UV-irradiated yeast and fungi was the historical vegan default because conventional D3 comes from lanolin in sheep wool. Lichen-derived cholecalciferol is now widely available and is genuinely D3, so a vegan diet no longer requires accepting the less efficient form. Check the source line on the label: lichen means vegan D3, lanolin means animal-derived D3, and yeast or fungal origin means D2.
- How much vitamin D should I take, and does the form change the number?
- The RDA is 600 IU (15 mcg) a day for adults up to 70 and 800 IU (20 mcg) beyond 70, with a tolerable upper intake level of 4,000 IU (100 mcg) a day (NIH Office of Dietary Supplements). The targets are not form-specific. What changes is efficiency: because D3 raises serum 25(OH)D further per microgram, the same labelled dose of D2 will move the blood number less, which is one reason prescription repletion courses using ergocalciferol rely on much larger doses.
Every claim, cited.
- [01]NIH Office of Dietary Supplements: Vitamin D Fact Sheet for Health Professionals. RDA 600 IU (15 mcg) to age 70 and 800 IU (20 mcg) beyond; upper limit 4,000 IU (100 mcg); D2 and D3 definitions and units.
- [02]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. Am J Clin Nutr 95(6):1357-64.
- [03]Tripkovic L, Wilson LR, Hart K, et al. 2017. Daily supplementation with 15 mcg vitamin D2 compared with vitamin D3 in healthy South Asian and white European women: a 12-wk randomized, placebo-controlled food-fortification trial. Am J Clin Nutr 106(2):481-490. n=335; D3 incremental advantage 15.3 and 16.0 nmol/L.
- [04]Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. 2011. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 96(7):1911-30. Context for high-dose ergocalciferol repletion protocols.
The Larderlab Team builds evidence-led frameworks for eating, lifting, and stocking a kitchen. We cite every claim. We publish the spreadsheet when possible. We buy what we review at retail price. When new data lands, we revise with a dated note.
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