Vitamin D2 vs D3 (2026): Which Should You Take?
D2 = ergocalciferol (plant/fungal); D3 = cholecalciferol (the form your skin makes from sunlight).
Not medical advice — this summarizes published research; if you were prescribed vitamin D2, talk to your doctor before switching. Methodology.
Take D3, not D2 — for almost everyone. Head-to-head, D3 raises blood vitamin D more efficiently: a 2024 meta-analysis of 20 trials found D2 raised 25(OH)D about 40% less than D3, even with daily dosing (PMID 37865222), and D3 lasts longer in the body. D2 still works — it isn't useless — it's just less efficient per dose. Choose D2 mainly if it's the high-dose form your doctor prescribed. Vegan? Look for lichen-derived D3, not D2.
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What's below: the head-to-head evidence for D3's ~40% edge (and an honest caveat that part of that gap is a lab-assay artifact), what vitamin D does and doesn't do (spoiler: it won't prevent cancer in healthy people), how to dose D3 safely without tipping into toxicity, and how to pick a product — including a vegan D3 that beats D2.
Head-to-Head Comparison
| Factor | Vitamin D2 | Vitamin D3 |
|---|---|---|
| Chemical name | Ergocalciferol | Cholecalciferol |
| Source | UV-irradiated yeast/fungi (vegan) | Lanolin (sheep wool), or lichen (vegan); made in skin from sunlight |
| Raising blood 25(OH)D | Works, but less per dose | More efficient — ~40% more than D2 in daily-dose trials (PMID 37865222) |
| Half-life | Shorter — cleared faster | Longer — steadier blood levels (PMID 17023693) |
| Natural to humans? | No — humans don't make D2 | Yes — your skin makes D3 from UVB |
| High-dose form | 50,000 IU (Rx Drisdol) | Up to 50,000 IU (OTC & Rx) |
| Vegan? | Yes | Lichen-derived D3 is vegan; most other D3 (lanolin) is not |
| Bottom line | Fine if prescribed; less efficient | The default for daily use |
The Evidence: Why D3 Is the Better Daily Choice
Multiple independent analyses reach the same conclusion — D3 raises serum 25-hydroxyvitamin D (the standard measure of vitamin D status) more than D2 at the same dose:
- A 2024 meta-analysis of 20 randomized trials found D2 raised total 25(OH)D about 10 nmol/L (~40%) less than D3, and importantly this held even with daily dosing — BMI was the strongest modifier, with the gap narrowing in heavier people (van den Heuvel 2024, PMID: 37865222).
- A separate 2021 meta-analysis (24 studies) reached the same verdict — D3 superior for total 25(OH)D by ~15.7 nmol/L (Balachandar 2021, PMID: 34684328) — and a 2017 daily-dosing RCT confirmed D3's edge specifically for everyday supplementation (Tripkovic 2017, PMID: 28679555), resolving an older question about whether D3's advantage held for daily (not just single large) doses.
- The likely mechanism: D2's metabolites bind vitamin D-binding protein less tightly, so D2 is cleared faster and produces a shorter, lower response (Houghton & Vieth 2006, PMID: 17023693 — a mechanistic review, not a trial).
One honest wrinkle worth knowing. Some clinical labs use blood tests that under-read the D2 metabolite, which can make D2 look even weaker than it truly is in real-world lab data (Garnett 2019, PMID: 31428669). The controlled trials above (using precise methods) still show a real D3 advantage — the point is just that the raw size of the gap can be partly an assay artifact, not only biology.
What Vitamin D Does — and Doesn't — Do
Correcting deficiency is worthwhile; disease prevention in healthy people isn't proven. It's easy to over-sell vitamin D. The large VITAL trial (25,000+ adults on D3 2,000 IU/day for ~5 years) found no reduction in cancer or major cardiovascular events (PMID: 30415629). Older pooled data hinted D3 (but not D2) might lower all-cause mortality (Cochrane 2014, PMID: 24414552), but that comes from pooling separate D2 and D3 trials — not a head-to-head test — so treat it as an open question, not a settled reason to pick D3. The solid case for D3 is efficiency at fixing a genuine deficiency, not preventing disease in people who already have enough.
Dosing Guide
| Situation | D3 Dose | Duration | Notes |
|---|---|---|---|
| Maintenance (not deficient) | 1,000-2,000 IU/day | Ongoing | Keeps adequate levels (RDA is 600-800 IU) |
| Mild deficiency (20-29 ng/mL) | 2,000-4,000 IU/day | 8-12 weeks, then retest | Most common scenario |
| Moderate deficiency (<20 ng/mL) | 4,000-5,000 IU/day | 8-12 weeks, then retest | Consider adding K2 at this dose |
| Severe deficiency (<10 ng/mL) | 50,000 IU/week (Rx) or 5,000-10,000 IU/day | 8-12 weeks, then retest | Under medical supervision |
| NIH tolerable upper limit | 4,000 IU/day | — | Higher only with testing/clinician guidance |
Get tested. Unlike magnesium (where blood tests are unreliable), the vitamin D blood test [25(OH)D] is accurate and widely available. Sufficiency is generally ≥20 ng/mL (some target 30+); below 20 ng/mL is deficient (IOM/Ross 2011, PMID: 21118827). A simple blood draw tells you your baseline.
More isn't better — respect the upper limit. Chronic intake well above 4,000 IU/day can cause vitamin D toxicity: a buildup of calcium in the blood (hypercalcemia) that causes nausea, excessive thirst and urination, weakness, and, over time, kidney stones or damage. Don't go above 4,000 IU/day without a blood test and clinician guidance, and retest your 25(OH)D before continuing a high dose. Because D2 and D3 doses are easy to mix up, double-check which one you're taking so you don't accidentally stack them.
Picking a D3 Product
Cost per day is pulled live from our product data. For a specific goal:
- Maintenance (2,000 IU): Nature Made Vitamin D3 2000 IU (USP-verified, $0.06/day) — simple and inexpensive.
- Correction (5,000 IU): Nature Made Vitamin D3 5000 IU (USP, $0.07/day) — one softgel.
- Vegan: Garden of Life Organics Vegan D3 Spray (1000 IU) ($0.12/day) — lichen-derived D3 (not D2), so you keep D3's efficiency.
See all seven ranked in our best vitamin D guide.
What About K2?
Vitamin K2 (menaquinone-7, MK-7) helps direct calcium to bones rather than arteries. High-dose vitamin D increases calcium absorption, so the theory is that adequate K2 helps route that calcium correctly.
- <2,000 IU/day D3: extra K2 is probably unnecessary if you eat some leafy greens or fermented foods.
- 4,000+ IU/day D3: adding K2 (100-200 mcg MK-7) is a reasonable precaution, and many D3 products bundle it.
See our detailed guide on vitamin D + K2.
Frequently Asked Questions
Is vitamin D2 or D3 better?
D3, for most people — it raises blood 25(OH)D more efficiently (D2 was ~40% lower in a 2024 meta-analysis of 20 trials, even daily; PMID: 37865222) and lasts longer in the body. D2 still corrects deficiency; it's just less efficient. Take D3 unless it's the high-dose form your doctor prescribed.
Why do doctors still prescribe vitamin D2?
Historical inertia — prescription vitamin D (Drisdol) is D2 at 50,000 IU and was the only high-dose option for decades. Equivalent D3 now exists OTC and by Rx; ask your doctor about switching.
Is there a vegan form of vitamin D3?
Yes — lichen-derived D3 is plant-based and the same cholecalciferol molecule, so you keep D3's efficiency over D2. That removes the old "take D2 if vegan" reason (D2 is also vegan, just less efficient).
Does vitamin D prevent cancer or heart disease?
Not in the general population — the large VITAL trial found no cancer or cardiovascular benefit from D3 (PMID: 30415629). Fixing a real deficiency is worthwhile; disease prevention in already-sufficient people isn't supported.
How much vitamin D3 should I take?
RDA 600 IU (800 over 70), sufficiency ≥20 ng/mL (PMID: 21118827). Maintenance 1,000-2,000 IU/day; correcting deficiency 4,000-5,000 IU/day for 8-12 weeks then retest. Upper limit 4,000 IU/day without clinician guidance.
Related Guides
- Vitamin D Dosage Guide — how much D3 by blood level
- Should You Take D3 with K2? — when to add K2 at higher doses
- Best Vitamin D Supplement — 7 products ranked
- Vitamin D Deficiency Signs · All Vitamin D Guides
Sources
- van den Heuvel EG, et al. "Comparison of the Effect of Daily Vitamin D2 and Vitamin D3 Supplementation on Serum 25-Hydroxyvitamin D Concentration: Systematic Review and Meta-Analysis." Adv Nutr. 2024;15(1):100133. PMID: 37865222
- Balachandar R, et al. "Relative Efficacy of Vitamin D2 and Vitamin D3 in Improving Vitamin D Status: Systematic Review and Meta-Analysis." Nutrients. 2021;13(10):3328. PMID: 34684328
- Tripkovic L, et al. "Daily supplementation with 15 µg vitamin D2 compared with vitamin D3... a 12-wk randomized food-fortification trial." Am J Clin Nutr. 2017;106(2):481-490. PMID: 28679555
- Tripkovic L, et al. "Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis." Am J Clin Nutr. 2012;95(6):1357-1364. PMID: 22552031
- Houghton LA, Vieth R. "The case against ergocalciferol (vitamin D2) as a vitamin supplement." Am J Clin Nutr. 2006;84(4):694-697. PMID: 17023693
- Garnett E, et al. "Efficacy of two vitamin D immunoassays to detect 25-OH vitamin D2 and D3." Pract Lab Med. 2019;17:e00130. PMID: 31428669
- Durrant LR, et al. "Vitamins D2 and D3 Have Overlapping But Different Effects on the Human Immune System." Front Immunol. 2022;13:790444. PMID: 35281034
- Bjelakovic G, et al. "Vitamin D supplementation for prevention of mortality in adults." Cochrane Database Syst Rev. 2014;(1):CD007470. PMID: 24414552
- Manson JE, et al. "Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease (VITAL)." N Engl J Med. 2019;380(1):33-44. PMID: 30415629
- Ross AC, et al. "The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine." J Clin Endocrinol Metab. 2011;96(1):53-58. PMID: 21118827
- NIH Office of Dietary Supplements. "Vitamin D: Fact Sheet for Health Professionals." ods.od.nih.gov