What is the Difference Between Vitamin D and Vitamin D3? A Nutritional Breakdown

October 4, 2025 •

2 min read

According to a 2025 study, vitamin D3 was more effective than D2 at increasing the transport of calcium to the bones. This distinction is key to understanding what is the difference between vitamin D and vitamin D3, and how each form contributes to your body's overall health.

Quick Summary

Vitamin D is an umbrella term for both D2 (from plants and fortified foods) and D3 (from sunlight and animal products). D3 is generally more potent and effective at raising and sustaining blood levels than D2, though both are vital for regulating calcium and promoting bone health.

Key Points

Two Primary Forms: Vitamin D exists in two main forms: vitamin D2 (ergocalciferol) from plants and D3 (cholecalciferol) from animals and sunlight.
Source Matters: D3 is naturally synthesized by your skin in response to sun exposure and found in animal products, while D2 is sourced from plants and fortified foods.
D3 is More Potent: Research indicates that vitamin D3 is more effective than D2 at increasing and sustaining vitamin D levels in the blood.
Absorption Mechanism: The body processes both D2 and D3, but D3 is metabolized more efficiently by the liver, leading to better bioavailability.
Essential for Health: Both forms are critical for promoting calcium absorption, maintaining bone health, supporting immune function, and regulating cell growth.
Supplement Choice: Due to its higher potency, vitamin D3 is the more commonly recommended form for supplements, though vegan D3 options are available.

The terms 'vitamin D' and 'vitamin D3' are often used interchangeably, leading to confusion. Vitamin D is a general term for fat-soluble vitamins, primarily vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). While both are essential, they differ in origin, absorption, and potency. Understanding these differences helps in making informed choices for health.

The Two Faces of Vitamin D: D2 vs. D3

Vitamin D2 (Ergocalciferol)

Vitamin D2 is mainly found in plants and fungi exposed to UV light and is often used to fortify foods. It's a common supplement choice for vegans.

Vitamin D3 (Cholecalciferol)

Vitamin D3 is produced in the skin from sun exposure and is present in animal-based foods like fatty fish and eggs. D3 is frequently used in supplements due to its effectiveness.

The Key Distinction: Potency and Bioavailability

Vitamin D3 is more effective than D2 at raising and maintaining vitamin D levels in the body. The liver processes D3 into calcifediol more efficiently, resulting in higher and more stable blood levels.

The Role of Vitamin D in the Body

Both forms of vitamin D, when converted to their active form (calcitriol), are vital for health. Vitamin D helps absorb calcium and phosphorus, crucial for bone health. It also supports immune function, muscle movement, cell growth, inflammation control, and cardiovascular health.

Comparison: Vitamin D2 vs. Vitamin D3


Feature	Vitamin D2 (Ergocalciferol)	Vitamin D3 (Cholecalciferol)
Source	Plants, fungi (e.g., mushrooms), and fortified foods	Sunlight on skin and animal-based foods (e.g., fatty fish, eggs)
Production	Produced by plants/fungi exposed to UV light	Produced by human skin exposed to UVB sunlight
Potency	Less potent at raising and maintaining blood levels	More potent and effective at sustaining blood levels
Availability	Prescription-strength supplements; some fortified foods	Commonly found in over-the-counter supplements
Suitability	Preferred for vegans or vegetarians	Preferred for most people seeking supplementation

Supplementation: Choosing the Right Form

For those needing supplements, D3 is often recommended due to its bioavailability and effect on blood levels. Vegan D3 from lichen is also available. Your healthcare provider can determine the best dosage based on a blood test.

Conclusion

Vitamin D includes both D2 and D3, but they differ in origin and potency. D3 is generally more effective at raising blood levels. Both are crucial for health, but D3 is often preferred for supplementation. Understanding these differences helps support bone health, immune function, and overall well-being. For more information, the National Institutes of Health provides fact sheets on vitamin D.

Frequently Asked Questions

No, they are not exactly the same. Vitamin D is an umbrella term that includes several types, most notably D2 and D3. Vitamin D3 (cholecalciferol) is one specific, highly effective form of vitamin D.

While both are beneficial, vitamin D3 is generally considered more effective at raising and maintaining vitamin D levels in the bloodstream than D2. Many healthcare professionals and supplement brands prefer D3 for this reason.

The main sources of vitamin D3 are sunlight exposure, where your skin produces it naturally, and animal-based foods, such as fatty fish (salmon, tuna), fish liver oils, and egg yolks.

Vitamin D2 is derived from plant sources like mushrooms, and it is also the form of vitamin D that is commonly used to fortify foods such as milk, cereals, and some orange juices.

Both D2 and D3 are inactive until they are processed by the body. The liver first converts them into calcidiol, and then the kidneys convert that into the active hormone, calcitriol.

Yes, while most D3 is animal-derived, some vegan vitamin D3 supplements are available. These are typically sourced from lichen, a symbiotic organism.

A blood test measuring the level of 25-hydroxyvitamin D (calcidiol) is the most accurate way to determine your body's vitamin D status. You can discuss getting tested with your doctor.

Vitamin D's most crucial function for bone health is facilitating the absorption of calcium from the digestive tract. Without it, the body cannot effectively use calcium to build and maintain strong bones, leading to conditions like osteoporosis.