What is Vitamin D2 Also Known As?

November 27, 2025 •

3 min read

According to the National Cancer Institute, vitamin D2 is a form of vitamin D that helps the body use calcium and phosphorus and is also known as ergocalciferol. This fat-soluble vitamin is primarily sourced from plants and fungi, in contrast to vitamin D3, which comes from animal sources and sun exposure. Understanding what is vitamin D2 also known as is crucial for those following specific dietary patterns, such as veganism, and for treating certain health conditions.

Quick Summary

Vitamin D2 is scientifically known as ergocalciferol, a plant-based vitamin produced by fungi upon UV exposure and used to fortify foods. It assists in calcium and phosphorus absorption, supporting bone health. Often prescribed for deficiency, it is processed in the liver and kidneys to become its active form, though some studies suggest it may be less potent than vitamin D3.

Key Points

Ergocalciferol is the Scientific Name: Vitamin D2 is most accurately and scientifically known as ergocalciferol, named for its plant precursor, ergosterol.
Plant and Fungal Origin: Unlike animal-sourced vitamin D3, ergocalciferol is derived from exposing fungi and yeast to ultraviolet (UV) light.
Essential for Bone Health: Both D2 and D3 are critical for bone health by promoting the absorption of calcium and phosphorus.
Supports Vegan Diets: Ergocalciferol is a primary source of vitamin D for vegans and vegetarians who do not consume animal-based foods.
Used Clinically for Deficiency: In higher, prescription doses, ergocalciferol is used to treat vitamin D deficiency and conditions like rickets.
Potential Differences from D3: Some research suggests that vitamin D3 might be more effective at raising and sustaining blood vitamin D levels, though both are used to treat deficiency.
Produced in UV-Exposed Mushrooms: Many mushrooms are commercially exposed to UV light to increase their vitamin D2 content, making them a significant dietary source.

Unpacking the Name: The Science Behind Ergocalciferol

Vitamin D, a family of fat-soluble vitamins, is crucial for calcium and phosphate regulation. Vitamin D2 is scientifically known as ergocalciferol. This name comes from its precursor, ergosterol, found in fungi and yeast. UV light exposure converts ergosterol to ergocalciferol.

Ergocalciferol is essential for bone and teeth strength by helping absorb calcium from the gut. It prevents rickets and osteomalacia caused by severe vitamin D deficiency. For vegans, ergocalciferol is a key plant-derived source of vitamin D.

The Origin and Production of Ergocalciferol

Ergocalciferol originates from plant sterols. Unlike animal-derived vitamin D3 (cholecalciferol), which forms in skin with sun exposure, ergocalciferol is synthesized differently.

UV Exposure: Fungi like mushrooms contain ergosterol.
Conversion: UV light converts ergosterol into ergocalciferol.
Biofortification: This process creates vitamin D-enhanced mushrooms, a significant dietary source of D2.

This production method makes ergocalciferol common in fortified foods and supplements for plant-based diets.

Vitamin D2 vs. D3: Understanding the Key Differences

Both vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) regulate calcium and phosphorus, but they differ in origin, metabolism, and potency.


Feature	Vitamin D2 (Ergocalciferol)	Vitamin D3 (Cholecalciferol)
Source	Plant and fungal based (e.g., UV-exposed mushrooms, yeast), fortified foods.	Animal-based (e.g., fatty fish, eggs) and produced in skin upon sun exposure.
Metabolism	Metabolized by the liver and kidneys, but studies suggest lower affinity to vitamin D-binding protein.	Generally considered more efficient at raising and maintaining serum vitamin D levels due to better binding affinity.
Potency	Some research indicates it may be less potent or have a shorter shelf-life than D3.	Often considered the more potent form for raising serum vitamin D levels in humans.
Availability	Available in supplements, fortified foods, and as a prescription drug (e.g., Drisdol®).	Widely available in over-the-counter supplements and many fortified dairy products.
Vegan Status	Always vegan as it is plant-derived.	Typically animal-derived, though vegan D3 from lichen is now available.

Why Do These Differences Matter?

Both D2 and D3 effectively treat vitamin D deficiency. However, some studies suggest D3 may be more efficient at raising blood levels. For vegans, D2 from fortified foods and supplements is a primary source. Those needing to quickly increase levels may be advised to take D3.

Health Benefits of Vitamin D2

Ergocalciferol offers numerous health benefits.

Bone Health: Like other vitamin D forms, it promotes calcium and phosphorus absorption for strong bones, preventing disorders and reducing fracture risk.
Immune System Support: Adequate vitamin D is linked to a healthy immune system, potentially reducing infection and autoimmune disease risk.
Vegan-Friendly Source: For vegans, ergocalciferol from fortified foods and mushrooms is a crucial source.
Treatment of Deficiency: Prescription ergocalciferol treats vitamin D deficiency and related conditions like rickets and hypoparathyroidism.

Conclusion: Navigating Your Vitamin D Needs

In conclusion, vitamin D2 is also known as ergocalciferol, a plant/fungus-sourced, fat-soluble vitamin vital for calcium and bone metabolism. While it serves the same purpose as D3 (cholecalciferol), they differ in origin, metabolism, and blood level efficacy. Ergocalciferol is crucial for vegans, found in fortified foods or supplements. Understanding these differences helps in making informed dietary choices and discussing supplementation with a healthcare provider.

MedlinePlus: Ergocalciferol

Further Information

A blood test for 25-hydroxyvitamin D levels helps determine individual vitamin D needs. Age, diet, location, and sun exposure influence requirements. High-dose prescription ergocalciferol may be used for severe deficiency. Supplements or fortified foods can help with daily maintenance. Always consult a health professional for personalized advice.

Frequently Asked Questions

The common and scientific name for vitamin D2 is ergocalciferol.

Ergocalciferol is produced by fungi and yeast when exposed to ultraviolet (UV) light. It is a plant-based form of vitamin D, unlike cholecalciferol (D3) which is found in animal products.

Yes, vitamin D2 is a suitable and common source of vitamin D for people on vegan and vegetarian diets, as it is derived from plant and fungal sources.

While both can treat vitamin D deficiency, some studies suggest that vitamin D3 is more effective at raising and maintaining overall vitamin D levels in the body due to differences in metabolism and binding efficiency. However, both forms are effective.

Yes, vitamin D2 can be found in certain foods, especially mushrooms that have been exposed to UV light, and in fortified foods like cereals and plant-based milks.

Yes, ergocalciferol is available by prescription for treating specific medical conditions related to severe vitamin D deficiency, such as rickets and hypoparathyroidism.

Although both are structurally similar, ergocalciferol (D2) and cholecalciferol (D3) differ in their side chains. Ergocalciferol has a double bond and a methyl group that are not present in cholecalciferol.