Skip to main content

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

Medically reviewed by Drugs.com. Last updated on April 8, 2024.

Official answer

by Drugs.com

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

Read next

Experts cannot say if oral vitamin D helps improve psoriasis symptoms, because overall, trial results have been mixed. While some open-label studies show a moderate to marked improvement (with some reports of remission), most double-blinded RCTs have shown only slight or no improvement. Supplementation could be considered on a case-by-case basis. Continue reading

Generally, it takes a few weeks of taking daily vitamin D supplements for vitamin D levels in the body to rise. Each 1,000 IU of vitamin D3 daily is expected to raise blood levels of 25(OD)D by 10 ng/ml after a few weeks. But it may take months to resolve symptoms of severe vitamin D deficiency such as rickets in children. It depends on how low your vitamin D levels were in the first place and some individual factors. Obesity, polluted environments, and malabsorption syndromes (such as Crohn’s disease) are just some factors that can increase the time it takes for vitamin D levels to work. Continue reading

You can raise your vitamin D levels quickly in three main ways, but it can take up to a week for increased vitamin D intake or exposure to be reflected in a vitamin D blood test: increasing your intake of foods that are naturally rich in vitamin D or fortified with vitamin D, taking a vitamin D supplement, or getting outside and exposing your skin to sunlight (although experts do not recommend this without sun protection). Continue reading

Related medical questions

Drug information

Related support groups

Medical Disclaimer