Vitamin D3 vs D2
Summary
Vitamin D comes as D3 (cholecalciferol) or D2 (ergocalciferol). Head-to-head trials and meta-analyses find D3 raises blood 25-hydroxyvitamin D more than D2 (grade A). In large trials of adults not selected for deficiency, vitamin D3 did not lower fracture rates or other major health events. Respiratory infections fell slightly (grade B). The adult upper limit is 4,000 IU/day.
Key facts
- Vitamin D3 (cholecalciferol, from lanolin or lichen) and vitamin D2 (ergocalciferol, from irradiated yeast)[1]
- Respiratory infections ↑ fewer, small (B); fractures ↔ (no effect); major health events in VITAL ↔ (no effect); bone density ↔, and lower at 4,000–10,000 IU/day ↓ (C)[11][6][8][12][7]
- 1 mcg vitamin D = 40 IU[1]
- RDA 600 IU (15 mcg), 800 IU (20 mcg) over 70; UL 4,000 IU (100 mcg)[1]
- Orlistat, statins, corticosteroids, thiazide diuretics; calcium with vitamin D and kidney stones[1]
- 7 graded human outcomes on this page
- October 9, 2026
How it works
EstablishedBoth D2 and D3 are converted in the liver to 25-hydroxyvitamin D, the blood marker of status, and then to the active hormone calcitriol, which increases calcium absorption from the gut (established). D2 supplementation lowers the D3-derived share of 25(OH)D, which is one proposed reason total 25(OH)D rises less with D2.[1][5]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Bones & joints | Grade A | Improved | RCT · n = 95 · 2013 | 4 rows |
| Immune | Grade B | Improved | Meta-analysis · n = 48,488 · 2021 | 1 row |
| Metabolic | Grade C | Mixed | RCT · n = 2,423 · 2019 | 1 row |
| Healthy aging | No effect | No effect | RCT · n = 25,871 · 2019 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Raising blood 25(OH)D: D3 vs D2 | Improved | Grade A | RCT · n = 95 · 2013 Healthy adults aged 18–50 in New Zealand over winter Form: vitamin D3 vs vitamin D2 vs placebo · Dose: 1,000 IU (25 mcg)/day · Duration: 25 weeks Total serum 25(OH)D was 21 nmol/L lower with D2 than with D3; D2 also lowered the 25(OH)D3 metabolite compared with placebo. | 23168298 (opens PubMed)Source [4] |
| Acute respiratory infections | Improved | Grade B | Meta-analysis · n = 48,488 · 2021 43 double-blind RCTs, ages 0–95 (primary-outcome data) Form: vitamin D3, D2 or 25(OH)D · Dose: Varied; benefit seen with daily 400–1,000 IU equivalents · Duration: Up to and over 12 months Slightly fewer people had one or more respiratory infections with vitamin D (61.3% vs 62.3%; OR 0.92). Benefit was clearer with daily dosing, 400–1,000 IU/day, durations of 12 months or less and ages 1–16. No difference in serious adverse events. | 33798465 (opens PubMed)Source [11] |
| Blood-sugar progression in adults with elevated blood sugar | Mixed | Grade C | RCT · n = 2,423 · 2019 Adults with prediabetes not selected for low vitamin D (D2d) Form: vitamin D3 · Dose: 4,000 IU/day · Duration: Median 2.5 years Diabetes occurred in 293 vs 323 participants (HR 0.88, 95% CI 0.75–1.04); not statistically significant. Adverse events did not differ. | 31173679 (opens PubMed)Source [9] |
| Bone density at high daily doses | Worsened | Grade C | RCT · n = 311 · 2019 Healthy adults aged 55–70 without osteoporosis, baseline 25(OH)D 30–125 nmol/L (Calgary) Form: vitamin D3 · Dose: 400 vs 4,000 vs 10,000 IU/day · Duration: 3 years Radial volumetric bone density fell more with 4,000 IU (-2.4%) and 10,000 IU (-3.5%) than with 400 IU (-1.2%); tibial density was lower only at 10,000 IU. No significant difference in estimated bone strength. | 31454046 (opens PubMed)Source [7] |
| Fractures | No effect | No effect | RCT · n = 25,871 · 2022 US men 50+ and women 55+ not selected for deficiency, low bone mass or osteoporosis (VITAL) Form: vitamin D3 · Dose: 2,000 IU/day · Duration: Median 5.3 years No significant effect on total fractures (HR 0.98), nonvertebral fractures (HR 0.97) or hip fractures (HR 1.01). No effect modification by baseline 25(OH)D. | 35939577 (opens PubMed)Source [6] |
| Major health events in healthy older adults (VITAL primary end points) | No effect | No effect | RCT · n = 25,871 · 2019 US men 50+ and women 55+, not selected for deficiency (VITAL) Form: vitamin D3 · Dose: 2,000 IU/day · Duration: Median 5.3 years No lower incidence of invasive cancer (HR 0.96) or major cardiovascular events (HR 0.97) vs placebo. Cancer death HR 0.83 (95% CI 0.67–1.02, not significant). No excess hypercalcemia. | 30415629 (opens PubMed)Source [8] |
| Bone mineral density (general adults) | No effect | No effect | Meta-analysis · n = 4,082 · 2014 23 RCTs in adults (92% women, mean age 59) without metabolic bone disease Form: vitamin D3 or D2 · Dose: Varied; 10 trials used under 800 IU/day · Duration: Mean 23.5 months Small benefit at the femoral neck only (+0.8%), with heterogeneity and possible bias toward positive results; no effect at the total hip, spine or other sites. | 24119980 (opens PubMed)Source [12] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Vitamin D3 (cholecalciferol) | Varies[1] | Well absorbed. Head-to-head RCTs and meta-analyses find D3 raises total 25(OH)D more than D2 and sustains it longer.[1][2][3][4] | Well tolerated at studied doses; excess intake over time can cause hypercalcemia (nausea, vomiting, weakness, kidney stones).[1] | Fractures, bone density, cancer and cardiovascular events, respiratory infections, prediabetes |
| Vitamin D2 (ergocalciferol) | Varies[1] | Well absorbed and raises its own metabolite, 25(OH)D2, about as well as D3 raises 25(OH)D3, but lowers 25(OH)D3, so total 25(OH)D rises less than with D3.[1][3][5] | Same hypercalcemia risk with excess intake.[1] | Mainly blood 25(OH)D comparisons; included in some respiratory-infection and bone-density trials |
Studied doses, daily needs and limits
Doses studied in human trials ranged from 400 to 10,000 IU/day of vitamin D3 (10 to 250 mcg/day), for 8 weeks to a median of 5.3 years. Some trials gave weekly amounts instead, such as 20,000 IU once a week.[7][5][6][10]
Intake reference: Adult RDA: 600 IU (15 mcg) per day through age 70, including pregnancy and breastfeeding; 800 IU (20 mcg) over 70. Adult UL: 4,000 IU (100 mcg) per day.[1] UL is lower for children (1,000–3,000 IU depending on age). The FNB noted toxicity is unlikely below 10,000 IU/day but that intakes under the UL might still have adverse effects over time. NIH ODS fact sheet (updated June 27, 2025).
Recommended intake and upper limit by age and sex
| Age | Male | Female | Pregnancy | Lactation | Upper limit (UL) |
|---|---|---|---|---|---|
| 0–6 months (AI) | 10 mcg | 10 mcg | — | — | 25 mcg |
| 7–12 months (AI) | 10 mcg | 10 mcg | — | — | 38 mcg |
| 1–3 years | 15 mcg | 15 mcg | — | — | 63 mcg |
| 4–8 years | 15 mcg | 15 mcg | — | — | 75 mcg |
| 9–13 years | 15 mcg | 15 mcg | — | — | 100 mcg |
| 14–18 years | 15 mcg | 15 mcg | 15 mcg | 15 mcg | 100 mcg |
| 19–50 years | 15 mcg | 15 mcg | 15 mcg | 15 mcg | 100 mcg |
| 51–70 years | 15 mcg | 15 mcg | — | — | 100 mcg |
| Over 70 years | 20 mcg | 20 mcg | — | — | 100 mcg |
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- OrlistatNIH fact sheetWith a reduced-fat diet, can reduce vitamin D absorption and lower 25(OH)D.[1]
- StatinsNIH fact sheetHigh vitamin D intakes might reduce the potency of these statins because both appear to share a metabolizing enzyme; statins may also reduce vitamin D synthesis.[1]
- Thiazide diureticsNIH fact sheetThiazides reduce urinary calcium loss; combined with vitamin D supplements this might lead to hypercalcemia, especially in older adults and people with reduced kidney function or hyperparathyroidism.[1]
Medicines that can lower levels
Other supplements
- CalciumNIH fact sheetIn the Women's Health Initiative, 1,000 mg calcium plus 400 IU vitamin D daily raised kidney-stone risk by 17% over 7 years (36,282 postmenopausal women). Shorter trials found more hypercalcemia and hypercalciuria but not more stones.[1]
Who should be careful
- Pregnancy and breastfeeding
- The RDA is the same as for other adults (600 IU), and the 4,000 IU UL applies. Higher amounts should be discussed with a clinician.[1]
- Kidney disease, kidney stones or high calcium
- Vitamin D raises calcium absorption. People with reduced kidney function, a history of kidney stones, hyperparathyroidism or high blood calcium face higher hypercalcemia risk, especially with thiazide diuretics.[1]
- High-dose use
- Toxicity is almost always from supplements: hypercalcemia, nausea, vomiting, muscle weakness, kidney stones and, in extreme cases, kidney failure and heart rhythm problems. A 3-year trial found lower bone density at 4,000–10,000 IU/day than at 400 IU/day.[1][7]
- Children
- ULs are lower for children: 1,000 IU (0–6 months) up to 3,000 IU (4–8 years); 4,000 IU from age 9.[1]
- Medicines
- See the interactions table: orlistat, statins, corticosteroids and thiazide diuretics are documented by NIH ODS.[1]
- Before you start
- Talk to your pharmacist or clinician before adding this supplement, especially if you take prescription medicines, are pregnant or breastfeeding, or have a chronic health condition.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Cost per studied dose, without the sales pitch
Compare any product you already have by the amount it delivers, not by capsule count or front-of-pack weight.
Cost per studied dose
Enter the price, servings and the amount per serving from your label.
Articles about Vitamin D3 vs D2
Plain-English answers to common questions, built on the evidence above.
Frequently asked questions
Is vitamin D3 better than D2?
For raising blood 25-hydroxyvitamin D, yes. Head-to-head trials and two meta-analyses find D3 raises total 25(OH)D more and keeps it higher longer; one 2024 analysis found daily D2 produced about 40% less rise. D2 is the plant- or yeast-derived form; lichen-derived D3 is an animal-free option.[2][3][1]
How many IU is 1 mcg of vitamin D?
1 mcg equals 40 IU. So 600 IU is 15 mcg, 1,000 IU is 25 mcg, 2,000 IU is 50 mcg and 4,000 IU (the adult upper limit) is 100 mcg.[1]
Can you get too much vitamin D?
Yes. The adult UL is 4,000 IU/day. Excess, almost always from supplements, can cause high blood calcium with nausea, vomiting, weakness and kidney stones. A 3-year trial found lower bone density at 4,000 and 10,000 IU/day than at 400 IU/day.[1][7]
Does vitamin D lower fracture risk?
Not in adults who are not deficient. In VITAL, 2,000 IU/day of D3 for a median 5.3 years did not reduce total, nonvertebral or hip fractures among 25,871 midlife and older adults. The trial did not test people with deficiency or osteoporosis.[6]
Does vitamin D help with colds and respiratory infections?
Slightly, on average. A 2021 meta-analysis of 43 trials found a small reduction in the share of people with at least one acute respiratory infection (61.3% vs 62.3%), clearest with daily doses of 400–1,000 IU.[11]
Do statins or steroids affect vitamin D?
NIH ODS notes corticosteroids such as prednisone can impair vitamin D metabolism, and high vitamin D intakes might reduce the potency of atorvastatin, lovastatin and simvastatin. Ask your pharmacist about your specific medicines.[1]
Sources
- [1]Vitamin D: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2025. fact-sheet
- [2]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. meta-analysis
- [3]Comparison of the Effect of Daily Vitamin D2 and Vitamin D3 Supplementation on Serum 25-Hydroxyvitamin D Concentration (Total 25(OH)D, 25(OH)D2, and 25(OH)D3) and Importance of Body Mass Index: A Systematic Review and Meta-Analysis.. Adv Nutr, 2024. meta-analysis
- [4]Long-term vitamin D3 supplementation is more effective than vitamin D2 in maintaining serum 25-hydroxyvitamin D status over the winter months.. Br J Nutr, 2013. RCT
- [5]Bioavailability of vitamin D(2) and D(3) in healthy volunteers, a randomized placebo-controlled trial.. J Clin Endocrinol Metab, 2013. RCT
- [6]Supplemental Vitamin D and Incident Fractures in Midlife and Older Adults.. N Engl J Med, 2022. RCT
- [7]Effect of High-Dose Vitamin D Supplementation on Volumetric Bone Density and Bone Strength: A Randomized Clinical Trial.. JAMA, 2019. RCT
- [8]Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease.. N Engl J Med, 2019. RCT
- [9]Vitamin D Supplementation and Prevention of Type 2 Diabetes.. N Engl J Med, 2019. RCT
- [10]Vitamin D and Risk for Type 2 Diabetes in People With Prediabetes : A Systematic Review and Meta-analysis of Individual Participant Data From 3 Randomized Clinical Trials.. Ann Intern Med, 2023. meta-analysis
- [11]Vitamin D supplementation to prevent acute respiratory infections: a systematic review and meta-analysis of aggregate data from randomised controlled trials.. Lancet Diabetes Endocrinol, 2021. meta-analysis
- [12]Effects of vitamin D supplements on bone mineral density: a systematic review and meta-analysis.. Lancet, 2014. meta-analysis
What changed
- First draft. Every evidence-row PMID checked with NCBI E-utilities (esummary + efetch abstract) and re-read in an independent adversarial pass.
- Added intake table from the NIH ODS fact sheet (checked Oct 9 2026), cost-per-studied-dose method, labeled analysis derived from cited rows.