What's the Difference Between Vitamin D3 and Just Regular Vitamin D?

October 15, 2025 •

3 min read

According to the Centers for Disease Control and Prevention (CDC), around 41% of U.S. adults are vitamin D deficient. For many, the road to correcting this deficiency is confusing, particularly when encountering the term 'vitamin D' alongside 'vitamin D3'. In reality, 'regular vitamin D' is an umbrella term encompassing several forms, with D3 being the more potent version produced by sunlight.

Quick Summary

Vitamin D is a group of fat-soluble vitamins, primarily consisting of D2 and D3. While D2 is plant-based and less stable, D3 is animal-based, more potent at raising blood levels, and produced naturally in the skin from sunlight. Both function similarly in the body, but D3 is often recommended for supplementation due to its higher effectiveness.

Key Points

Not a Single Vitamin: 'Regular' vitamin D is a catch-all term for several related compounds, primarily D2 and D3.
Source Matters: Vitamin D3 comes from sun exposure and animal products, while D2 is plant-based and found in some fortified foods.
Superior Potency: D3 is significantly more effective and potent than D2 at increasing and sustaining vitamin D blood levels.
Metabolism Difference: The body metabolizes D3 more efficiently, leading to better overall vitamin D status.
Supplement Choice: D3 is often the preferred form for supplementation unless a person is vegan, in which case a lichen-based D3 or D2 is an option.
Expert Recommendation: Many health experts recommend D3 for correcting deficiencies due to its superior efficacy.
Dietary Role: Fatty fish, eggs, and fortified products are key dietary sources of vitamin D.

Understanding the 'Regular' Vitamin D

Vitamin D is not a single compound

Before distinguishing D3, it's crucial to understand that 'regular vitamin D' isn't a single nutrient, but a family of related compounds. The two most important forms for human health are vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Both forms are precursors, meaning they must be converted by the liver and kidneys into the active hormone, calcitriol, before they can be used by the body.

Vitamin D2 (Ergocalciferol)

Also known as ergocalciferol, vitamin D2 is the plant-based form. It is produced when ergosterol, a compound found in fungi and yeasts, is exposed to ultraviolet (UV) radiation. Many fortified foods, such as certain cereals, plant-based milks (like soy and almond milk), and mushrooms, contain vitamin D2 because it is often cheaper to produce. However, some evidence suggests that D2 is not as effective as D3 at raising and maintaining the body's overall vitamin D levels.

The Natural Potency of Vitamin D3

Vitamin D3 (Cholecalciferol)

Vitamin D3, or cholecalciferol, is the version of vitamin D that is naturally produced by the human body. When our skin is exposed to sunlight (specifically UVB rays), it synthesizes D3 from a cholesterol precursor. This is why vitamin D is often referred to as the 'sunshine vitamin'. In addition to sunlight, D3 is found in animal-based foods, including fatty fish, fish liver oils, egg yolks, and beef liver.

The key difference in effectiveness

While both D2 and D3 effectively treat vitamin D deficiency, numerous studies have shown that D3 is significantly more potent and efficient at raising and sustaining blood levels of 25-hydroxyvitamin D—the primary marker of vitamin D status. It is also more stable and has a longer shelf life. For this reason, healthcare professionals often recommend vitamin D3 for supplementation, as it offers a superior ability to correct deficiencies.

Comparison Table: Vitamin D2 vs. Vitamin D3


Feature	Vitamin D2 (Ergocalciferol)	Vitamin D3 (Cholecalciferol)
Source	Primarily from plants (fungi, yeast) and fortified foods.	Sunlight exposure and animal-based foods.
Natural Origin	Plant-based, produced when fungi or yeast are irradiated with UV light.	Produced naturally by the body when skin is exposed to UVB radiation.
Effectiveness	Less potent at raising blood vitamin D levels and may not sustain levels as long as D3.	More effective at increasing and maintaining blood vitamin D levels over time.
Chemical Stability	Less stable and has a shorter shelf life compared to D3.	More stable, with a longer shelf life.
Vegan-Friendly	Yes, as it is derived from plant and fungi sources.	No, unless specifically sourced from lichen or algae.
Common Use	Often found in fortified foods and some supplements, sometimes prescribed.	Most recommended form for supplementation due to higher efficacy.

Making an Informed Choice

For most people, the decision between D2 and D3 depends on their dietary choices and health goals. Those following a strict vegan diet may prefer D2 or a plant-based D3 sourced from lichen. However, for those seeking the most effective supplement to raise and maintain vitamin D levels, D3 is the clear winner. It's always best to consult with a healthcare provider to determine the right dosage and form of supplementation based on your individual needs and current vitamin D status.

Conclusion: Distinguishing the Differences

While 'regular vitamin D' is a broad term encompassing both D2 and D3, the key difference lies in their source, potency, and effectiveness. D3 is the form naturally produced by the body with sun exposure and found in animal products, and it is significantly more effective at increasing and sustaining vitamin D levels in the blood. D2, on the other hand, is plant-derived and less potent. Understanding this crucial distinction empowers consumers to make better-informed decisions about their dietary intake and supplementation to support overall health.

For more detailed scientific comparisons and studies on vitamin D metabolism, refer to the National Institutes of Health's Office of Dietary Supplements fact sheet on Vitamin D: https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/.

Frequently Asked Questions

No, vitamin D is a general term for a group of related nutrients, including vitamin D2 and vitamin D3. D3 is a specific, more effective form of vitamin D.

Research indicates that vitamin D3 is more effective at raising and maintaining healthy blood levels of vitamin D for longer periods compared to vitamin D2.

Vitamin D2 (ergocalciferol) is the plant-based form of vitamin D. It is derived from fungi and yeast and is often used to fortify foods.

Your body produces vitamin D3 naturally when your skin is exposed to sunlight. It is also found in animal-based foods like fatty fish, fish liver oil, and egg yolks.

For most people, vitamin D3 is recommended for supplements due to its higher potency and effectiveness in raising and sustaining blood vitamin D levels.

Traditional D3 is animal-derived, but vegan-friendly D3 sourced from lichen or algae is now available. Alternatively, vegans can use vitamin D2 supplements.

Fortified foods can contain either vitamin D2 or D3. D2 is more common because it is cheaper to produce, but checking the nutrition label is the best way to be sure.

Yes, it is possible to take too much vitamin D, which can lead to high calcium levels in the blood. Always follow recommended dosage guidelines from a healthcare provider.