Vitamin D2 vs D3

Short answer: NIH ODS says vitamin D2 and D3 are both well absorbed and both raise serum 25(OH)D, but most evidence shows D3 raises 25(OH)D more and keeps it higher for longer.

Form	What ODS says	Notes
D2 (ergocalciferol)	Made by UV irradiation of ergosterol in yeast. Raises 25(OH)D, but less and for a shorter time than D3.	Not animal-derived.
D3 (cholecalciferol)	Usually made from 7-dehydrocholesterol in lanolin; an animal-free lichen version also exists. Raises and keeps 25(OH)D higher.	Vegans can look for lichen-sourced D3.

Units: 1 mcg vitamin D = 40 IU. The adult RDA is 15 mcg (600 IU), 20 mcg (800 IU) over 70; the UL from age 9 (including pregnancy and breastfeeding) is 100 mcg (4,000 IU).

D2 and D3 count toward the same upper limit. Our dose comparisons convert IU at 40 IU = 1 mcg.

Sources

NIH ODS: Vitamin D – Health Professional Fact Sheet

This page only paraphrases the sources above and is not medical advice. If you are pregnant, breastfeeding, take medicines or have a chronic condition, ask a doctor or pharmacist first.

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For information only; not medical advice. Talk to a doctor or pharmacist before starting or stopping any supplement.