What Form of Vitamin D Is Best: D2 vs. D3 Explained

October 26, 2025 •

3 min read

According to the NIH, an estimated 50% of the population may have a vitamin D deficiency, making supplementation a common consideration for many. Deciding what form of vitamin D is best, however, can be confusing given the options available.

Quick Summary

This article explains the key differences between vitamin D2 and D3, detailing their sources, effectiveness, and how different supplement types impact absorption to help you make an informed choice.

Key Points

Vitamin D3 is more effective than D2: Studies show that cholecalciferol (D3) is more potent and raises blood levels for a longer duration than ergocalciferol (D2).
Absorption is enhanced with fat: Since vitamin D is fat-soluble, it is best absorbed when taken with a meal containing healthy fats, regardless of the form.
Supplement form can aid absorption: Liquid vitamin D may offer faster absorption, making it beneficial for those with digestive issues or difficulty swallowing pills.
Vegans can find D3: Plant-based vitamin D3 sourced from lichen is available and works similarly to animal-derived D3, making it a viable option for vegans.
K2 and D3 work together: Taking vitamin D3 with K2 is recommended by some experts, as K2 helps direct calcium to the bones and prevents buildup in arteries.
Consult a professional before supplementing: Always speak with a healthcare provider to determine your vitamin D needs and proper dosage, as excess vitamin D can be harmful.

The Core Difference: D2 vs. D3

When choosing a vitamin D supplement, the primary distinction is between vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). While both can help correct a deficiency, their origins and metabolic pathways differ, influencing their overall efficacy in the human body.

Vitamin D2 (Ergocalciferol)

Vitamin D2 is the plant-based form, primarily found in UV-irradiated mushrooms and yeast. It is also the type of vitamin D often used to fortify foods, such as milk and cereal, due to its lower cost of production. However, research suggests D2 is less effective at raising and maintaining long-term blood vitamin D levels compared to D3. Some studies even indicate that D2 supplementation might decrease levels of D3 in the body.

Vitamin D3 (Cholecalciferol)

Vitamin D3 is the form that is naturally synthesized in the skin of humans and animals when exposed to sunlight. It is also found in animal-sourced foods like fatty fish, egg yolks, and beef liver. Numerous studies have shown D3 to be more potent and longer-lasting than D2, making it the preferred choice for most doctors and nutrition experts for supplementation. Vegan-friendly D3 is also now widely available, sourced from lichen.

The Role of Vitamin K2

An increasingly popular strategy is to pair vitamin D3 with vitamin K2. Vitamin D3 increases calcium absorption, but vitamin K2 plays a crucial role in directing that calcium to the bones and teeth, preventing it from depositing in soft tissues and arteries. This synergistic relationship can improve bone and cardiovascular health, though it is not recommended for individuals on blood-thinning medication.

Maximizing Vitamin D Absorption

Beyond choosing the right form, how you take your vitamin D matters. Since vitamin D is fat-soluble, its absorption is significantly enhanced when consumed with a meal containing healthy fats, such as olive oil, avocado, or nuts. This is why many supplements suspend vitamin D3 in a lipid base, like MCT oil or olive oil, to improve bioavailability.

Supplement Format: Capsule vs. Liquid

Vitamin D is available in various formats, and each has unique benefits.

Capsules (or Softgels): These offer a convenient, pre-measured dose and are tasteless. They have a long shelf life and are highly portable, making them ideal for individuals with a consistent routine. Softgels, which contain an oil base, are often preferred for better absorption.
Liquid (Drops/Sprays): These are an excellent alternative for people who struggle to swallow pills, including children and older adults. Liquid forms, especially those using nanoparticle or liposomal technology, can offer faster absorption by bypassing certain digestive barriers, which can be beneficial for individuals with malabsorption issues. The dosage is also easily adjustable, which is useful when following a doctor's specific recommendations.

Which Form is Best for You? A Comparison Table


Feature	Vitamin D2 (Ergocalciferol)	Vitamin D3 (Cholecalciferol)
Source	Plant-based (yeast, mushrooms)	Animal-based (fatty fish, eggs) and sunlight exposure
Availability	Prescription (high dose), fortified foods	Over-the-counter, animal-based foods, some vegan sources
Effectiveness	Less potent, shorter-acting in the body	More potent, raises and sustains levels longer
Vegan Option	Yes, naturally derived	Yes, derived from lichen
Primary Use	Can correct deficiency, but often secondary choice	Preferred for supplementation due to higher efficacy

Conclusion: Making the Best Choice for Your Health

When considering what form of vitamin D is best, the evidence strongly points to vitamin D3 as the most effective for raising and maintaining blood levels. However, individual needs and preferences are also important factors. For vegans, animal-free D3 sourced from lichen is an excellent option. Those with digestive issues or difficulty swallowing might benefit from liquid or spray formulations for enhanced absorption. For optimal absorption, always take your vitamin D with a fatty meal. Finally, consider discussing the inclusion of vitamin K2 with your healthcare provider for enhanced bone and cardiovascular support. Always consult a medical professional before starting any new supplement regimen to determine the correct dosage for your specific needs.

For more detailed information on vitamin D, consult the Office of Dietary Supplements at the National Institutes of Health. [^1]

[^1]: Office of Dietary Supplements, National Institutes of Health. "Vitamin D - Health Professional Fact Sheet." https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/

Frequently Asked Questions

Vitamin D2 (ergocalciferol) comes from plant sources like mushrooms, while vitamin D3 (cholecalciferol) comes from animal sources and is also produced in the skin from sun exposure.

Most evidence suggests that vitamin D3 is more effective than D2 at raising and maintaining adequate vitamin D levels in the blood.

Liquid vitamin D may be absorbed faster, which can benefit individuals with malabsorption issues, swallowing difficulties, or those needing a more flexible dosage. However, capsules and softgels are generally more convenient and stable.

Vitamin D3 aids in calcium absorption, while vitamin K2 helps ensure that calcium is deposited in the bones and teeth instead of accumulating in soft tissues like arteries.

To improve absorption, take your vitamin D supplement with a meal that contains healthy fats, such as avocado or olive oil. Many supplements are already suspended in an oil base for this reason.

Yes, vegans can find vitamin D3 supplements derived from lichen, which is a plant-based source. This vegan D3 is as effective as animal-derived D3.

Sunlight is an excellent source of vitamin D, but factors like geographic location, skin tone, and season can limit production. Many people require supplements to maintain optimal levels, especially during winter months.