What Is Vitamin D2? 

Vitamin D2, also called ergocalciferol, is a fat-soluble form of vitamin D. It helps the body absorb calcium and phosphorus, supports normal bone mineralization, and contributes to healthy muscle and cellular function. Vitamin D2 is mainly produced from ergosterol, a compound found in fungi and yeast. It is commonly available in mushrooms, fortified foods, dietary supplements, and some prescription preparations. Unlike vitamin D2, humans naturally produce vitamin D3 in the skin when exposed to UVB radiation. 

Vitamin D2 vs. Vitamin D3 

Vitamin D2 and D3 perform similar functions, but they differ in their sources and effectiveness in raising blood vitamin D levels. 

Feature	Vitamin D2	Vitamin D3
Scientific name	Ergocalciferol	Cholecalciferol
Main source	Fungi and yeast	Skin and animal sources
Produced by human skin	No	Yes
Found in supplements	Yes	Yes
Vegan options	Common	Lichen-derived D3
Main function	Calcium & phosphorus metabolism	Calcium & phosphorus metabolism
Blood Vitamin D levels	Effective	Often more effective

Research generally suggests that Vitamin D3 may raise and maintain blood 25(OH)D levels more effectively than Vitamin D2, although both are biologically active forms of Vitamin D. 

How Does Vitamin D2 (Ergocalciferol) Work? 

After vitamin D2 is absorbed, the body converts it into metabolites that participate in vitamin D metabolism. 

The simplified process is 

Vitamin D2 → Liver → 25(OH)D → Kidney → Active Vitamin D 

Active vitamin D helps regulate calcium and phosphorus and increases their absorption from the intestine. 

Read more about Vitamin D1

Health Benefits of Vitamin D2 

Vitamin D2 contributes to several important functions, particularly bone and mineral health. 

Health Benefit	How It Helps
Supports strong bones	Helps absorb calcium and phosphorus needed for normal bone mineralization.
Improves calcium absorption	Helps the intestine absorb calcium needed for bones, muscles, and nerves.
Supports phosphorus balance	Helps regulate phosphorus absorption and mineral metabolism.
Supports muscle function	Adequate Vitamin D contributes to normal muscle function.
Supports immune function	Participates in normal immune regulation.
Supports cellular function	Vitamin D metabolites influence various cellular processes.

Severe vitamin D deficiency can contribute to rickets in children and osteomalacia in adults. 

Vitamin D2 Food Sources 

Natural vitamin D2 is particularly associated with fungi. UV-exposed mushrooms can contain significantly more vitamin D2 than untreated mushrooms. 

The main dietary sources include: 

Food Source	Vitamin D2 Information
UV-exposed mushrooms	One of the best natural food sources
UV-treated mushrooms	May contain higher amounts of vitamin D2
Regular mushrooms	Usually contain less vitamin D2
Fortified plant-based milk	May contain added vitamin D
Fortified cereals	May contain added vitamin D
Other fortified foods	Amount varies by product.

Always check the nutrition label because vitamin D content varies between products. 

Vitamin D2 for Vitamin D Deficiency 

Vitamin D2 can be used to prevent or treat vitamin D deficiency. The appropriate dose depends on the person’s Vitamin D status, age, health condition, and reason for treatment. 

Common risk factors for deficiency include: 

• Limited sun exposure 

• Low dietary Vitamin D intake 

• Older age 

• Obesity 

• Malabsorption 

• Certain gastrointestinal conditions 

• Certain liver or kidney disorders 

• Some medications 

A blood test measuring 25-hydroxyvitamin D [25(OH)D] is commonly used to assess vitamin D status. 

How Much Vitamin D2 Should You Take? 

There is no single dose suitable for everyone. Routine supplements commonly contain 400–2,000 IU, while higher doses may be prescribed to treat confirmed deficiency. 

A dose of 50,000 IU may sometimes be prescribed for vitamin D deficiency, but it should not be taken routinely without medical supervision. 

The appropriate dose can depend on blood vitamin D levels, age, medical conditions, kidney function, and other factors. 

Vitamin D2 Safety and Side Effects 

Vitamin D is fat-soluble, so excessive supplementation can cause vitamin D toxicity and hypercalcemia, or abnormally high calcium levels in the blood. 

Possible symptoms include: 

• Nausea and vomiting 

• Constipation 

• Excessive thirst 

• Frequent urination 

• Weakness 

• Confusion 

• Loss of appetite 

• Kidney stones or kidney problems 

The NIH lists 100 mcg (4,000 IU) per day as the tolerable upper intake level for adults and children aged 9 years and older. Higher doses may sometimes be prescribed temporarily for medical treatment. 

Who Should Be Careful With Vitamin D2? 

Extra medical guidance may be needed for people with kidney disease, kidney stones, hypercalcemia, hyperparathyroidism, sarcoidosis, or conditions that affect vitamin D metabolism. 

Vitamin D can also interact with certain medicines. 

Medication	Possible Concern
Thiazide diuretics	May increase the risk of high calcium levels.
Digoxin	High calcium may increase the risk of abnormal heart rhythms.
Corticosteroids	Can affect calcium and vitamin D metabolism.
Orlistat	May reduce absorption of vitamin D.

If you regularly take prescription medication, discuss high-dose vitamin D supplementation with a healthcare professional. 

Research on Vitamin D2

Research continues to compare vitamin D2 and D3, investigate their metabolism, and determine how different doses affect vitamin D status.

A systematic review and meta-analysis published in 2021 evaluated the relative effectiveness of vitamin D2 and D3 and found that D3 generally had a greater effect on serum 25(OH)D concentrations. However, both forms can increase vitamin D levels.

Frequently Asked Questions