Vitamin D3 vs Vitamin D2: What Is the Difference?
Executive Summary
Cholecalciferol and ergocalciferol compared: where each comes from, how they are measured, and which form UK supplements usually contain.
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Vitamin D3Clinical (cholecalciferol) is the form made in human skin and found in animal-source foods; vitamin D2 (ergocalciferol) comes from yeast and UV-treated mushrooms. Both raise blood 25-hydroxyvitamin D, and both count towards the UK recommendation of 10 micrograms (400 IU) a day. Most supplements sold in the UK use D3.
Where each form comes from
Vitamin D3Clinical (cholecalciferol) is produced in skin exposed to UVB and is present in oily fish, egg yolk, liver and red meat. In supplements it is usually extracted from lanolin (sheep wool grease) or, for vegan products, from lichen.
Vitamin D2 (ergocalciferol) is produced when ergosterol in yeast or fungi is exposed to UV light. It is inherently plant-based and is the form used in some fortified foods and in certain prescribed preparations.
Are they equivalent?
Both are metabolised in the liver to 25-hydroxyvitamin D, the circulating form measured on a blood test. Comparative studies have generally found D3 raises and maintains 25-hydroxyvitamin D levels more effectively than an equal dose of D2, particularly with intermittent dosing. UK dietary guidance treats total vitamin D intake as a single figure and does not set separate recommendations by form.
For most people taking a modest daily amount, either form contributes. If you are choosing between two products at the same strength and price, D3 is the pragmatic choice unless you need a plant-based product, in which case look for lichen-derived D3 or a D2 product.
Reading the label
- Check the amount in micrograms and IU — 25 µg is 1,000 IU.
- Check the form: cholecalciferolClinical (D3) or ergocalciferol (D2).
- Check suitability: lanolin-derived D3 is suitable for vegetarians but not vegans; lichen-derived D3 and D2 are suitable for vegans.
- Check the carrier: tablets, softgels in oil, and sprays all work; vitamin DClinical is fat-soluble, so taking it with a meal containing some fat is sensible.
Authorised claims apply to the nutrient
Health claims for vitamin D — such as its contribution to the maintenance of normal bones and to the normal function of the immune system — apply to vitamin D as a nutrient, at qualifying levels, regardless of whether it is supplied as D2 or D3.
Related reading
References and further reading
- Vitamin D — NHS. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/ (accessed 26 August 2026)
- SACN vitamin D and health report — GOV.UK. https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report (accessed 26 August 2026)
- Vitamin D — British Nutrition Foundation. https://www.nutrition.org.uk/nutritional-information/vitamins-and-minerals/ (accessed 26 August 2026)
Article sources
Our editorial team references guidance from independent public health bodies and peer-reviewed research. Links open in a new tab.
- Vitamin D — Health Professional Fact Sheet — NIH Office of Dietary Supplements
- Vitamin D — NHS
- Vitamin D: Is more always better? — Mayo Clinic
- Vitamins and minerals overview — NHS
- Dietary Supplement Fact Sheets — NIH Office of Dietary Supplements
- Healthy Lifestyle — Mayo Clinic
How we reviewed this article
- Medical reviewer
- Prof MM Althaf, MD, FRCP(UK), FASN, MSc.
- Last reviewed
- 26 August 2026
- Next review due
- 26 August 2027
Written by the Vitamin Vitality editorial team from independent public-health guidance and peer-reviewed research, then checked by our medical reviewer. Articles are re-checked at least every 12 months, or sooner when guidance changes. Read our editorial & medical review policy.
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