What it is
Vitamin D comes in two supplement forms, D2 and D3, and the animal question is all about how each is made. The NIH Office of Dietary Supplements spells out the default source of D3.
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vitamin D3 is typically produced with irradiation of 7-dehydrocholesterol from lanolin obtained from the wool of sheep
Lanolin is the grease from sheep's wool, so standard D3 is animal-derived. The good news is that a vegan D3 now exists, and D2 sits outside the problem entirely because it is made from yeast or fungi.
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An animal-free version of vitamin D3 sourced from lichen is also available
How to choose
For a fortified food or a supplement, the label rarely states the source of its D3, so a product carrying a vegan mark, a lichen-derived claim, or plainly listing D2 is the safe pick. When none of that is printed, the sourcing genuinely varies, and the fact sheet is blunt about the fix.
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People who avoid all animal-sourced products can contact dietary supplement manufacturers to ask about their sourcing and processing techniques.
How it is made
Cholecalciferol is manufactured by exposing 7-dehydrocholesterol to UV-B light and then applying heat to finish the conversion. The standard feedstock for that precursor is lanolin, the wax scoured out of sheep’s wool, which is the entire reason D3 is a vegan question at all. Vitamin D2, ergocalciferol, follows the same UV logic but starts from ergosterol in yeast or mushrooms. One ingredient, sheep against fungus, is the whole difference.
Since around 2012 a second D3 route has been commercial. Certain lichens, which are partnerships of fungus and alga, carry their own 7-dehydrocholesterol, extracted and irradiated exactly like the lanolin version. The molecule that comes out is identical cholecalciferol and the body cannot tell them apart. Bulk-market D3 in fortified milk, gummies and supermarket multivitamins is still overwhelmingly lanolin-sourced, while a growing set of brands carrying Vegan Society or Vegetarian Society approval use lichen instead.
The D2 question
D2 and D3 are not interchangeable in the body, which is what makes this awkward rather than simple. The NIH’s health professional fact sheet states that most evidence shows D3 raises and sustains blood 25-hydroxyvitamin D more than D2, even though gut absorption is similar. A 2021 systematic review and meta-analysis in Nutrients put the gap at a mean 15.7 nmol/L greater rise for D3. So a vegan who wants the more effective form faces a real trade-off: D2 is automatically vegan and the weaker performer, and stronger D3 traces to a sheep unless the label says lichen.
How to tell
Ergocalciferol or vitamin D2 on a label is a safe default. Cholecalciferol or vitamin D3 needs a second look for the words lichen, algal or vegan D3, or a Vegan Society, Vegetarian Society or Certified Vegan mark. Fortified foods are the blind spot: some plant milks, cereals, juices and calcium chews use D3 rather than D2, and the ingredient line just reads vitamin D3. Multivitamin gummies catch people out twice, because the gelatin gets flagged and the D3 inside does not. High-dose prescription D3 is typically lanolin-derived too.