Vitamin D3 vs D2: Which Form Should You Take? (2026)

Vitamin D3 (cholecalciferol) raises blood levels of vitamin D more effectively than vitamin D2 (ergocalciferol) and maintains those levels for longer. A systematic review and meta-analysis in Nutrients confirmed that D3 is more efficacious than D2 at raising serum 25-hydroxyvitamin D. Both forms work through the same biochemical pathway and both treat deficiency, but D3 does the job more efficiently — which is why it is the form recommended in most clinical guidelines and found in most quality supplements. If you are choosing a supplement, D3 is the practical first choice.

Key Takeaways

• D3 (cholecalciferol) comes from animal sources and is the form the skin makes from sunlight. D2 (ergocalciferol) comes from plants, yeast and mushrooms.
• Multiple meta-analyses confirm D3 raises and sustains blood 25(OH)D levels more effectively than D2.
• Both forms are converted to the same active vitamin D hormone in the body (calcitriol), but D3 is the more efficient precursor.
• The NIH makes no distinction between D2 and D3 in its RDA, but most evidence-based guidelines prefer D3 for supplementation.
• Vegans can use lichen-derived D3, which is cholecalciferol from a plant source — equally effective to animal-derived D3.
• Both forms are fat-soluble and absorb best when taken with a meal containing fat.

Where Each Form Comes From

Vitamin D2 is produced by plants, yeast and fungi when exposed to ultraviolet light. Mushrooms are the primary food source of D2, and it is also used in some fortified foods and most prescription vitamin D preparations (because it has been available in high-dose pharmaceutical form longer than D3).

Vitamin D3 is produced in animal skin — including human skin — when UVB radiation reacts with a compound called 7-dehydrocholesterol. It is found in fatty fish, egg yolks and liver, and is the form used in most over-the-counter supplements. A plant-derived version of D3 is made from lichen and is widely available for vegans.

How Both Forms Work in the Body

Both D2 and D3 are inactive precursors that must be converted before the body can use them. After absorption from the gut, both are taken to the liver, where they are converted to 25-hydroxyvitamin D (25(OH)D) — the form measured in blood tests. From there, the kidneys convert 25(OH)D to calcitriol (1,25-dihydroxyvitamin D), the active hormone that regulates calcium absorption, immune function, muscle function and gene expression.

The key difference is how efficiently each precursor is converted to 25(OH)D in the liver and how long the resulting metabolite stays in the circulation. D3 produces 25(OH)D3, which has a longer half-life and appears to bind more tightly to vitamin D binding protein, explaining why D3-supplemented people maintain higher blood levels over time.

What the Evidence Shows

The systematic review and meta-analysis in Nutrients (2021) concluded that cholecalciferol (D3) is more efficacious than ergocalciferol (D2) at raising serum 25(OH)D levels, with the difference more pronounced at higher doses. Several individual randomised controlled trials have reached the same conclusion.

At the same time, both forms are effective at correcting deficiency. The difference is one of efficiency rather than a binary works/does not work distinction. A 2025 study found that D3 was more efficient at inducing the expression of genes responsible for calcium absorption. A critical review noted that part of the measured difference in some assays may be due to cross-reactivity in the tests themselves, but the practical conclusion from most researchers is still to prefer D3 when choosing a supplement.

For what low vitamin D actually looks like in the body, see our guide on the 7 warning signs of vitamin D deficiency.

Daily Needs and Upper Limits

The NIH does not distinguish between D2 and D3 in its RDA, recommending 600 IU per day for adults up to age 70 and 800 IU for those over 70. The upper tolerable intake level is 4,000 IU per day. Both forms count equally toward these targets. For more detail on dosing including for deficiency, hair loss and constipation, see our guides on vitamin D3 and K2 benefits and whether vitamin D causes constipation.

When to Choose D2 Over D3

D2 has legitimate uses. It is the form prescribed in many countries at high doses (50,000 IU capsules) for treating severe deficiency, because pharmaceutical-grade ergocalciferol has been available longer than high-dose D3 products. D2 is also the natural choice for strict vegans who cannot use lichen-derived D3 or who prefer to source their supplement from yeast or fungi.

UV-exposed mushrooms are a food-based D2 source worth knowing about. Placing mushrooms gill-side up in direct sunlight for 30 to 60 minutes can significantly increase their D2 content. The NIH notes that half a cup of raw white mushrooms provides around 46 percent of the daily value — though levels vary considerably by growing conditions.

Vegan Vitamin D: Lichen-Derived D3

For vegans who want D3’s better performance without animal products, lichen-derived cholecalciferol is the answer. Lichen (a symbiotic fungus and alga organism) produces D3 — not D2 — when exposed to UV light, making it the one plant-based source of the same molecule the human skin makes. It is widely available in supplement form and is equally effective to animal-derived D3.

Practical Tips for Supplementing

• Choose D3 for everyday supplementation — it is more effective per microgram and maintains levels for longer.
• Take it with a meal containing fat — both forms are fat-soluble and absorb significantly better with dietary fat.
• Get your level tested before choosing a high dose. A blood 25(OH)D test is the only way to know whether you are deficient or replete and how much supplementation is needed.
• Pair D3 with K2 for bone health — K2 activates the proteins that direct calcium to bones rather than arteries. Our guide on vitamin K2 benefits explains this in full.
• If prescribed D2 at high dose by a doctor, take it as directed — prescription D2 at therapeutic doses effectively corrects deficiency even if D3 is more efficient.

Frequently Asked Questions

Is D3 always better than D2?

For everyday supplementation, yes — D3 raises blood levels more effectively and keeps them elevated longer. The difference is most pronounced at higher doses. For acute treatment of severe deficiency under medical supervision, prescription D2 is effective and widely used.

Can vegans take vitamin D3?

Yes — lichen-derived D3 is vegan-certified cholecalciferol that performs the same as animal-derived D3. It is widely available in health shops and online.

Are D2 and D3 measured the same way in blood tests?

Both produce 25(OH)D metabolites that standard blood tests detect, though some older assays read them at slightly different efficiencies. Most modern tests accurately capture both forms. If your supplement is D2, your doctor should know this when interpreting results.

Does the difference matter at the RDA level?

The difference is most meaningful at higher doses and in people who are significantly deficient. At the modest 600 to 800 IU RDA, both forms will cover maintenance needs for most adults, though D3 still has a small efficiency advantage. The practical reason to prefer D3 for daily use is consistency of effect.

Final Thoughts

The evidence consistently points toward D3 as the more effective form for daily supplementation — it raises blood vitamin D levels more efficiently and sustains them longer than D2. For vegans, lichen-derived D3 delivers the same cholecalciferol molecule from a plant source. D2 still works and remains the form used in many prescription-strength products, so if you have been prescribed D2 by a doctor, take it as directed. For anyone choosing between the two on a pharmacy shelf, D3 is the straightforward choice.

This article is for educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment.