Supplements
D3 (cholecalciferol) raises and sustains blood 25-hydroxyvitamin D more effectively than D2 (ergocalciferol), and it is the default choice for almost everyone. D2 remains relevant for strict vegans without access to lichen-derived D3, and in high-dose prescription form. Our top pick is Nature Made Vitamin D3 1000 IU.
How We Picked
We judged this on the outcome that matters: how much each form raises serum 25-hydroxyvitamin D and how long it holds, drawing on head-to-head randomised comparisons and meta-analysis. Product selection then followed source — a mainstream D3 for most people, and two vegan D2 options for those who need a plant-derived form.
A. Nature Made Vitamin D3 1000 IU — Best Overall
Nature Made Vitamin D3 1000 IU
Nature Made
- Cholecalciferol (D3) form
- 1,000 IU per softgel
- USP verified
- Oil-based softgel aids absorption
- Very low cost per day
Why we picked it: One thousand IU is the dose most adults should actually be taking day to day, and USP verification is the strongest available check on what is in the softgel. The oil base helps absorption of a fat-soluble vitamin.
B. DEVA Vegan Vitamin D2 2400 IU — Best Vegan D2
DEVA Vegan Vitamin D2 2400 IU
DEVA
- Plant-derived ergocalciferol
- 2,400 IU per tablet
- Certified vegan
- No animal-derived excipients
- Registered with the Vegan Society
Why we picked it: For strict vegans who cannot source lichen-derived D3, D2 is the workable alternative — it does raise blood levels, just less efficiently. Certification here covers the excipients as well as the active ingredient.
C. Vitamatic Vegan Vitamin D2 2400 IU — Best Value D2
Vitamatic Vegan Vitamin D2 2400 IU
Vitamatic
- Ergocalciferol from plant sources
- High tablet count per bottle
- Low cost per serving
- Vegan and gluten free
- Simple tablet format
Why we picked it: Because D2 is less potent unit for unit, cost per tablet matters more than usual — you may need a higher intake to reach the same blood level. Bulk counts make that practical.
The Short Answer
Take D3 unless you have a specific reason not to. Both forms are converted in the liver to 25-hydroxyvitamin D, the storage form measured on blood tests, but D3 does it more efficiently and the resulting metabolite persists longer. A widely cited meta-analysis comparing the two concluded that D3 is more effective at raising serum 25(OH)D, with the gap especially pronounced when doses are given weekly or monthly rather than daily.
Where They Come From
D3 (cholecalciferol) is what human skin produces from UVB exposure. Commercially it is made from lanolin in sheep's wool, which is why most D3 is not vegan — though lichen-derived vegan D3 is now widely available and is the better option for plant-based diets. D2 (ergocalciferol) is produced by irradiating ergosterol from yeast or fungi. Mushrooms exposed to UV light are the main food source of D2, and it is the form used in most high-dose prescription products in the United States.
Why D3 Holds Better
Two mechanisms explain the difference. D3 binds vitamin D binding protein more tightly than D2, so it stays in circulation longer rather than being cleared. And 25-hydroxyvitamin D2 appears to be catabolised faster than the D3 metabolite. The practical result is that a given dose of D3 produces a higher peak and a slower decline. If you take vitamin D daily the gap narrows somewhat; if you take a large dose weekly or monthly, D3's advantage is substantial.
When D2 Still Makes Sense
Three situations. Strict veganism where lichen-derived D3 is unavailable or unaffordable — D2 does work, it simply requires more of it. Prescription high-dose therapy: 50,000 IU weekly ergocalciferol is a standard treatment for deficiency in the United States and is effective at that dose. Fortified foods: some plant milks and cereals use D2, and it still contributes to intake. D2 is not useless; it is second choice.
Dose, Testing and the Upper Limit
The recommended intake for adults is 600 IU (15 mcg) daily, rising to 800 IU after 70, with a tolerable upper limit of 4,000 IU. Most people supplementing do well on 1,000–2,000 IU. If you are using D2, you may need proportionally more to reach the same blood level. Deficiency is defined as serum 25(OH)D below 12 ng/mL, with 20–50 ng/mL considered sufficient. Above 50 ng/mL there is no demonstrated additional benefit. Note that some laboratory assays measure D2 and D3 metabolites separately — ask for total 25(OH)D. Our vitamin D supplements guide covers dosing in more depth.
What Vitamin D Does and Does Not Do
Vitamin D is essential for calcium absorption and bone mineralisation, and correcting a deficiency has clear benefits for bone health and muscle function. What the large trials did not find is prevention of cancer or cardiovascular events in people who were not deficient — the VITAL trial tested 2,000 IU daily in nearly 26,000 adults and came back negative on both. A later analysis did show reduced incidence of autoimmune disease. Supplement to correct a shortfall, and pair with K2 and magnesium if you want the fuller picture — see vitamin D3 K2.
Frequently Asked Questions
Is vitamin D3 better than D2?
For raising and maintaining blood levels, yes. Meta-analysis of head-to-head comparisons shows D3 (cholecalciferol) increases serum 25-hydroxyvitamin D more effectively than D2 (ergocalciferol) and sustains it longer, with the gap widest when doses are given weekly or monthly rather than daily.
Is vitamin D3 vegan?
Usually not. Most commercial D3 is derived from lanolin in sheep's wool. However, lichen-derived vegan D3 is now widely available and is the better choice for plant-based diets than switching to D2, since it combines vegan sourcing with D3's superior potency.
Why do doctors prescribe vitamin D2?
The standard high-dose prescription product in the United States is 50,000 IU ergocalciferol, taken weekly, and it works effectively at that dose for correcting deficiency. The prescription formulation predates much of the D2 versus D3 comparison research and remains in common use.
How much vitamin D2 equals D3?
There is no single conversion factor, but D2 is meaningfully less effective unit for unit at raising and sustaining blood levels, particularly with intermittent dosing. If you use D2, a higher intake and follow-up blood testing are sensible to confirm you have reached the sufficient range.
Quick Comparison
| Product | Key Feature | Best For |
|---|---|---|
| Nature Made Vitamin D3 1000 IU | USP verified D3 at a sensible everyday dose | Best Overall |
| DEVA Vegan Vitamin D2 2400 IU | Certified vegan ergocalciferol | Best Vegan D2 |
| Vitamatic Vegan Vitamin D2 2400 IU | Bulk vegan D2 at the lowest cost per tablet | Best Value D2 |
Bottom Line: Which Should You Buy?
For most people: the Nature Made Vitamin D3 1000 IU. USP verified D3 at a sensible everyday dose
Runner-up: the DEVA Vegan Vitamin D2 2400 IU. Certified vegan ergocalciferol
Also great: the Vitamatic Vegan Vitamin D2 2400 IU. Bulk vegan D2 at the lowest cost per tablet
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Sources & Research
This article was informed by peer-reviewed research and clinical guidelines. The Supplements Corner Editorial Team reviews published literature to ensure accuracy.
Dosage Reference
Recommended intake for adults is 600 IU (15 mcg)/day, rising to 800 IU (20 mcg)/day over age 70; the tolerable upper limit is 4,000 IU (100 mcg)/day. Typical supplemental doses are 1,000–2,000 IU/day of D3. Prescription ergocalciferol for deficiency is commonly 50,000 IU weekly under medical supervision. Serum 25(OH)D below 12 ng/mL indicates deficiency and 20–50 ng/mL is sufficient. Take with a fat-containing meal. Consult a doctor before use if you have hypercalcaemia, sarcoidosis or kidney disease.
Key Studies Referenced:
- Tripkovic L, et al. (2012). "Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. American Journal of Clinical Nutrition."
- Armas LAG, Hollis BW, Heaney RP (2004). "Vitamin D2 is much less effective than vitamin D3 in humans. Journal of Clinical Endocrinology & Metabolism."
- Manson JE, et al. (2019). "Vitamin D supplements and prevention of cancer and cardiovascular disease (VITAL). New England Journal of Medicine."
Medical Disclaimer: This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement regimen. Individual results may vary.
