Usually not. US regulation defines vitamin D3, cholecalciferol, as occurring in and isolated from fish liver oils, or manufactured from cholesterol, both of which are animal-derived. Vitamin D2, ergocalciferol, is defined as produced from ergosterol isolated from yeast and related fungi, which is not. Vegan D3 does exist, made from lichen, but it is a claim a manufacturer makes rather than something the name D3 implies.

Is vitamin D3 vegan? Usually not, and D2 is

Most origin questions on this site need a detour through manufacturing, because a regulation defines a substance and stays quiet about where it came from. Vitamin D is the exception, and the answer is sitting in the number.

What the regulation says

D2, ergocalciferol, is “produced by ultraviolet irradiation of ergosterol isolated from yeast and related fungi”.

D3, cholecalciferol, “occurs in, and is isolated from, fish liver oils. It is also manufactured by ultraviolet irradiation of 7-dehydrocholesterol produced from cholesterol.”

Fungi on one side. Fish liver oil or cholesterol on the other. So the default answer for D3 is that it is animal-derived, and the default answer for D2 is that it is not.

The exception, which is a claim

Lichen-derived D3 exists and is genuinely vegan. It is also a thing a manufacturer states, prominently, because it is the reason someone would choose their product over a cheaper one.

The rule that follows is the standing one on this site: the claim tells you something and its absence tells you nothing. A bottle saying vegan D3 has made a statement it is accountable for. A bottle saying cholecalciferol has not made any statement at all about origin, and the regulation’s default is the one to assume.

Certification carries this further than a self-declared claim does, for the reasons the page for people avoiding animal ingredients sets out.

The second question, which catches people

Getting the vitamin right does not finish the job, because the capsule is a separate ingredient.

Softgel capsules are very often Gelatin, made from pig or cow collagen. So a lichen-sourced D3 inside a gelatin softgel is not a vegan product, and both facts are in the same ingredient list a few words apart.

The plant alternative is a hypromellose capsule, made from cellulose, and manufacturers who use it say so for the same reason they say lichen.

The short version

D2 is fungal. D3 is animal-derived unless the label says lichen. The capsule is a second question and often the one that decides it. And whether D2 and D3 are equivalent for raising your levels is a clinical matter with a real literature behind it, which this page deliberately does not attempt to settle.