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Vitamin D

How to Compare Vitamin D Supplements

Units, D2 vs D3, source, totals across products and cost per 1,000 IU.

Updated September 28, 20261 min readBy the SuppScout Editorial Team
The short answer

Compare vitamin D products by amount in mcg (and IU), form (D2 or D3), source (lanolin, lichen, yeast), other ingredients, and cost per 1,000 IU. Add up vitamin D across everything you take — multivitamins and fortified foods count.

Key takeaways
  • 1 mcg = 40 IU.
  • D3 raised blood levels more than D2 in pooled trials.
  • Upper limit for ages 9+ is 100 mcg (4,000 IU)/day.

Units

Labels list micrograms; many also show IU. 25 mcg = 1,000 IU; 50 mcg = 2,000 IU; 125 mcg = 5,000 IU.

D2 or D3

Both raise vitamin D levels; D3 did so more effectively in a 2012 meta-analysis. See D2 vs D3.

Source

Most D3 is from lanolin; vegan D3 is from lichen; D2 is from yeast or fungi.

Add up your total

The UL (100 mcg / 4,000 IU per day for ages 9+) applies to all sources combined. Higher amounts should be supervised by a clinician.

VITAMIN D

D2 vs D3

Sources, vegan status and what research says about raising levels.

Compare →

Sources & references

  1. Vitamin D: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.govGovernment
  2. Tripkovic L, Lambert H, Hart K, et al. (2012). Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. American Journal of Clinical Nutrition 95(6). doi:10.3945/ajcn.111.031070Meta-analysis

SuppScout links to primary and authoritative sources wherever possible. See our editorial policy for how sources are selected and how corrections are handled.

This page is educational and is not medical advice. Talk to a healthcare professional before starting a supplement, especially if you have a medical condition, take medications, or are pregnant or breastfeeding.