Vitamin D2 vs. Vitamin D3: Differences and Supplement Choices

If you have picked up a vitamin D supplement, you have probably seen two versions on the shelf: D2 and D3. Both are forms of vitamin D, and both can raise the level of vitamin D in your blood, but they are not identical. This comparison explains what each one is, where it comes from, what research suggests about how they differ, and what to look for on a label. It does not recommend a dose, since the right amount depends on your health, diet, and medicines.

This page compares two nutrient forms rather than branded products, so it contains no purchase links. For background on the vitamin itself, read Vitamin D Explained.

What Is Vitamin D2?

Vitamin D2, called ergocalciferol, is made by plants and fungi when they are exposed to ultraviolet light. Mushrooms exposed to UV light and some fortified foods and supplements contain D2. It is also the form in some prescription high-dose vitamin D products.

What Is Vitamin D3?

Vitamin D3, called cholecalciferol, is the form that human skin makes when exposed to sunlight. It is found in animal foods such as fatty fish, egg yolks, and liver, in many fortified foods, and in most over-the-counter supplements. Supplement D3 is usually made from lanolin (from sheep's wool), and vegan D3 made from lichen is also available.

Comparison Table

Feature	Vitamin D2 (ergocalciferol)	Vitamin D3 (cholecalciferol)
Chemical form	Ergocalciferol	Cholecalciferol
Common sources	UV-exposed mushrooms, some fortified foods	Fatty fish, egg yolk, liver, fortified foods; made by human skin from sunlight
Supplement availability	Less common over the counter; used in some prescription products	Very common in over-the-counter supplements
Origin	Plants and fungi	Animals (lanolin) or lichen for vegan products
Evidence on raising blood levels	Raises 25(OH)D levels	Raises 25(OH)D levels, and several analyses suggest more effectively or for longer, though the clinical importance is debated
Safety considerations	Upper limit and interactions are the same as D3	Upper limit and interactions are the same as D2

What Does Research Say About the Differences?

The NIH Office of Dietary Supplements (ODS) states that both D2 and D3 raise blood levels of vitamin D, and notes that D3 might raise levels higher and maintain them longer than D2 in some studies, while some research finds the two to be similar, particularly when D2 is given daily instead of in large occasional doses. A meta-analysis of randomized trials by Tripkovic and colleagues (2012) concluded that D3 was more effective than D2 at raising blood levels of 25-hydroxyvitamin D, but the clinical relevance for bone and health outcomes is not settled.

What this means in practice:

• Both can correct low levels if taken as directed.
• D3 is more widely sold and more widely used in research.
• Choosing between them is often a matter of diet (vegan or not), prescription, and availability.
• Higher blood levels do not automatically mean better health.

Reading Supplement Labels

Check:

1. Which form is listed: D2, D3, or "vitamin D" without the form.
2. Amount per serving, in micrograms (mcg) and international units (IU). 1 mcg equals 40 IU.
3. Percent Daily Value, which is based on 20 mcg (800 IU).
4. Serving size. Some gummies and liquids need several servings to reach the amount on the front.
5. Other ingredients, such as calcium, vitamin K, or vitamin A, which add to your total.
6. Source: lichen-derived D3 for vegans, and gelatin in capsules or gummies.
7. Third-party testing and expiry date.

See our guide to reading a supplement label.

Dosing and Risks of Excessive Intake

We do not recommend an individual dose. For general context, the ODS gives the RDA as 600 IU (15 mcg) a day for most adults up to age 70 and 800 IU (20 mcg) after 70, with a tolerable upper intake level of 4,000 IU (100 mcg) a day for adults. Doses above this are sometimes prescribed by doctors for diagnosed deficiency and should be taken only under supervision.

Too much vitamin D, from either form, can cause high blood calcium (hypercalcemia), nausea, vomiting, weakness, frequent urination, and kidney problems. Count vitamin D from all sources, including multivitamins and fortified foods, and be careful with liquid drops where measuring errors are easy.

Medication Interactions

The same cautions apply to both forms. Ask a doctor or pharmacist if you take:

• corticosteroids such as prednisone
• orlistat or cholestyramine
• seizure medicines such as phenytoin or phenobarbital
• thiazide diuretics
• digoxin

Also ask if you have kidney disease, sarcoidosis, hyperparathyroidism, or a history of kidney stones.

When Professional Advice Is Appropriate

Talk to a healthcare professional if:

• you are considering a supplement and take medicines or have a medical condition;
• you have symptoms such as bone pain or muscle weakness;
• you are in a higher-risk group, such as older adults, people with malabsorption conditions, or breastfed infants (ask the pediatrician);
• you have been prescribed vitamin D and wonder whether to switch forms (do not replace a prescription without asking); or
• you want a blood test to check your level.

Frequently Asked Questions

Is D3 better than D2?

Some research suggests D3 raises blood levels more effectively, but both work, and the importance for health outcomes is not settled.

Can vegans take D3?

Yes, if it is made from lichen. D2 is also plant-based. Check the label.

Can I switch from D2 to D3?

Ask your healthcare provider first if the D2 was prescribed.

Which is in fortified milk?

It depends on the product. Check the label, as fortification can use D2 or D3.

Is more vitamin D better?

No. Excessive amounts can cause harm.

Final Thoughts

Both vitamin D2 and D3 can raise vitamin D levels. D3 is more common and may be a bit more efficient in some studies, but that does not make D2 a bad choice, particularly for people who need a plant-based or prescription option. The most important decisions are the amount, the interactions, and whether you need a supplement at all.

Medical Disclaimer

This comparison is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. It is not a recommendation for any dose. Consult a qualified healthcare professional before taking vitamin D supplements.

References and Further Reading

• NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Consumers
• NIH Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals
• Tripkovic L, et al. (2012). Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. American Journal of Clinical Nutrition.