Vitamin D2

Also known as ergocalciferol, vitamin d-2.

Last reviewed October 9, 2026 · Jump to references

What is Vitamin D2?

In plain words

Vitamin D2 is a form of vitamin D made when ultraviolet light acts on a substance in fungi or yeast. The liver and kidneys turn it into an active form that helps the body absorb calcium and maintain bones. Researchers study its role in correcting low vitamin D levels and supporting bone health. Too much can cause dangerously high calcium levels and damage the kidneys.

Technical definition

Vitamin D2 (ergocalciferol) is a fat-soluble secosteroid vitamin produced by ultraviolet irradiation of ergosterol found in fungi and yeast. It undergoes hydroxylation in the liver and primarily the kidneys to form active 1,25-dihydroxyvitamin D2, which binds the nuclear vitamin D receptor and regulates gene expression involved in calcium and phosphate balance and bone mineralization. It is available in dietary supplements and in approved prescription products in the United States.

Educational information only. This page does not provide medical advice or determine whether a supplement is appropriate for you. Review supplements with a qualified healthcare professional, especially if you take medication, are pregnant, have surgery scheduled, or have a chronic medical condition.

Evidence by use

Each use is rated on its own. There is no single overall effectiveness score.