Vitamin D3 vs D2: What the Difference Means on a Label
D3 (cholecalciferol) is the form made in skin and found in animal foods, usually lanolin-derived in supplements though lichen-derived versions exist. D2 (ergocalciferol) is produced from yeast or fungi. They are not treated as equivalent unit for unit, and the form is named on the panel rather than the front.
Two forms of vitamin D are sold as supplements. They are not the same molecule, they are not derived from the same sources, and they are not treated as equivalent at the same number of international units.
What each one is
Vitamin D3 (cholecalciferol) is the form made in human skin on exposure to UVB, and the form found in animal-source foods. In supplements it is most commonly derived from lanolin, the wax from sheep’s wool. It is also produced from lichen, which is the route used for products suitable for vegans.
Vitamin D2 (ergocalciferol) is produced from yeast or fungal sources by UV irradiation. It is inherently plant-derived, and it is the form used in some prescription preparations.
Are they interchangeable?
Not straightforwardly. Both raise circulating vitamin D, but the two forms have been compared in trials and reviews and are generally not treated as equivalent unit for unit. The NIH fact sheet discusses the comparison directly, and it is worth reading rather than taking a summary from a retailer.
The practical consequence for a shopper is narrow: if you are switching between products, note which form you were taking, because a like-for-like IU swap is not necessarily like for like.
If you avoid animal products
This is where the distinction matters most concretely. Standard D3 from lanolin is an animal-derived ingredient. The two options are lichen-derived D3, which will say so prominently because it is a selling point, or D2. A product that simply says “vitamin D3” with no source stated is most likely lanolin-derived.
Our vitamin D comparison carries a Dietary filter where products state vegan or vegetarian suitability on the label.
Reading the panel
The form is named in the ingredients or in brackets after the nutrient — “Vitamin D3 (as cholecalciferol)”. If a label says only “Vitamin D” with no form, that is a disclosure gap worth noting.
See also IU vs mcg and vitamin D with K2.