What it is and where it comes from
Most vitamin D3 is made from lanolin, the natural grease in sheep wool, which is taken without killing the sheep. Some is made from fish liver oil, and vegan D3 from lichen. Vitamin D2 comes from yeast or mushrooms. In supplements and fortified foods, D3 often sits in a gelatin softgel or a gelatin-coated powder.
Where you find it
Vitamin supplements, drops, fortified milk, plant milks, margarine and breakfast cereals.
What to look for on the label
Choose tablets, drops in oil, vegetable capsules, or a halal or vegan label. Vegan D3 from lichen and vitamin D2 avoid the question.
This is a guide, not a fatwa. Recipes change, so check the label, look for halal certification, and ask your local imam where scholars differ.