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Vitamin D1 vs D2 vs D3: What's the difference between them?

Medically reviewed by Last updated on April 8, 2022.

Official answer


The term "Vitamin D" now refers to several different forms. The two forms important in humans are: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is a synthetic form (man made) and Vitamin D3 is the internal form that we make.

German researcher Adolf Windaus first discovered 3 forms of vitamin D, which he called D1, D2, and D3. It was later learned that the vitamin D1 was a mixture of compounds rather than a pure vitamin D product, so the term D1 is no longer used.

Read Next → The Vitamin D Guide

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