Vitamin D2 vs D3: Which Form Raises Vitamin D Levels Better?

A vitamin D label can make the choice look deceptively simple.

One bottle lists vitamin D2, or ergocalciferol. Another contains vitamin D3, or cholecalciferol. The number of micrograms may be identical, yet the two forms do not always produce identical changes in vitamin D status.

Both work. Both are absorbed in the intestine. Both can raise circulating vitamin D.

But if the question is narrower — which form generally raises blood levels of vitamin D more effectively? — the evidence increasingly points in one direction.

Vitamin D2 vs D3: key facts

Are vitamin D2 and D3 absorbed differently?

Not in the simple way supplement marketing sometimes implies.

Both vitamin D2 and D3 are well absorbed in the small intestine. Dietary fat can improve absorption, although vitamin D can still be absorbed without fat.

The meaningful difference appears after absorption.

Vitamin D obtained from supplements, food or sunlight must be metabolized before it becomes biologically active. One of the important intermediate products is 25-hydroxyvitamin D, or 25(OH)D, which is the blood marker most commonly used to evaluate vitamin D status.

That is where D2 and D3 begin to separate.

The NIH Office of Dietary Supplements notes that both forms increase 25(OH)D, but most evidence indicates that vitamin D3 produces a greater increase and maintains the higher concentration for longer.

So it is more accurate to say that the two forms differ in their effect on vitamin D status than to claim that one simply “absorbs” and the other does not.

For the basics of how vitamin D from sunlight, food and supplements fits together, see Bextera’s Vitamin D guide and Vitamin D ingredient dossier.

How much stronger is vitamin D3?

There is no single percentage that applies to every person, dose and dosing schedule.

That is one reason broad statements such as “D3 is twice as good” are not particularly useful.

A 2024 systematic review and meta-analysis compared vitamin D2 and D3 across 20 comparative studies. Across the daily-dose comparisons measured using comparable laboratory methods, the increase in total 25(OH)D was lower in the vitamin D2 groups than in the vitamin D3 groups.

The weighted difference was about 10.39 nmol/L in favor of D3 in those comparisons.

The analysis also showed why individual response cannot be reduced to the supplement form alone. Baseline vitamin D status, body mass index and other factors influenced the results, and substantial heterogeneity existed between studies.

That is an important qualification.

D3 generally performs better when the outcome is the rise in total 25(OH)D, but that does not mean every person taking D3 will achieve a particular blood level or that an identical dose will produce an identical response in two people.

What did newer research find about vitamin D2?

A 2025 systematic review looked at a slightly different question.

Rather than simply comparing total vitamin D status after D2 and D3 supplementation, researchers examined what happens specifically to circulating 25(OH)D3 when vitamin D2 is given.

Across the randomized trials included in the meta-analysis, vitamin D2 supplementation was associated with lower 25(OH)D3 concentrations compared with controls that did not receive D2.

That finding has prompted interest in whether increasing one vitamin D metabolite may affect the metabolism or clearance of another.

But the authors were appropriately cautious. They concluded that more research is needed to determine whether those metabolic differences should change clinical recommendations.

In other words, the study adds useful biological context. It does not prove that vitamin D2 is ineffective or harmful.

That distinction matters because both D2 and D3 remain capable of increasing total vitamin D status.

Where do D2 and D3 come from?

The difference also matters for people who care about how a supplement is produced.

Vitamin D2 is generally made by exposing ergosterol from yeast to ultraviolet light.

Vitamin D3 has traditionally been produced from 7-dehydrocholesterol derived from lanolin, which comes from sheep’s wool.

That means conventional D3 is not always suitable for someone avoiding animal-derived ingredients.

However, vegan vitamin D3 made from lichen is now available, so choosing a plant-compatible supplement no longer necessarily means choosing vitamin D2.

The form and the source should therefore be treated as two separate label questions.

A product can contain D3 and still use an animal-free source.

Does the number on the label matter more than D2 versus D3?

The amount matters, but it needs context.

The FDA Daily Value for vitamin D is 20 micrograms, equivalent to 800 IU. That is the reference used to calculate the percentage Daily Value on U.S. Nutrition and Supplement Facts labels.

It is not the same thing as a personalized treatment target.

The Recommended Dietary Allowance is 15 micrograms, or 600 IU, for most adults through age 70 and 20 micrograms, or 800 IU, for adults older than 70.

Supplements often contain amounts above those figures.

That does not automatically make a higher-dose product better. Vitamin D requirements, existing status, sun exposure, diet, age, medical conditions and clinician-directed treatment can all affect why a particular amount is being used.

For comparing products on the shelf, Bextera would therefore look at:

1. vitamin D per serving;
2. whether the form is D2 or D3;
3. the source of the vitamin;
4. serving frequency;
5. percent Daily Value;
6. other ingredients;
7. independent testing or manufacturing evidence.

The full label matters more than the biggest number printed on the front.

Is vitamin D3 always the better choice?

“Better” depends on what is being measured.

If the question is:

Which form generally raises and maintains serum 25(OH)D more effectively?

The evidence favors vitamin D3.

If the question is whether vitamin D2 can raise vitamin D status, the answer is also yes.

And if a clinician has prescribed or recommended a specific form or dose to treat a documented deficiency, that clinical context matters more than a general supplement comparison.

It is also important not to turn a difference in a laboratory marker into a claim that D3 automatically produces better outcomes for every health condition. Raising 25(OH)D and demonstrating a clinically meaningful benefit are not the same research question.

That is particularly relevant with vitamin D, where supplements have been studied for a very wide range of conditions with mixed results.

Bottom line

Vitamin D2 and D3 are both legitimate forms of vitamin D, and both can increase vitamin D status. The distinction is not simply marketing, though: current evidence consistently shows that vitamin D3 generally raises serum 25(OH)D more effectively and maintains those concentrations longer than vitamin D2.

For an ordinary supplement comparison, that gives D3 an evidence-based advantage.

But form is still only one part of the label. Dose, baseline vitamin D status, source, serving schedule and the reason someone is taking vitamin D all affect how useful that comparison ultimately is.

Sources

• NIH Office of Dietary Supplements — Vitamin D Fact Sheet for Health Professionals
• U.S. Food and Drug Administration — Daily Value on Nutrition and Supplement Facts Labels
• Advances in Nutrition — systematic review and meta-analysis comparing vitamin D2 and vitamin D3
• Nutrition Reviews — 2025 systematic review and meta-analysis of vitamin D2 supplementation and 25(OH)D3