Vitamin D2 vs D3
Vitamin D2 (ergocalciferol) and D3 (cholecalciferol) compared: what trials show about blood levels, what they do not show about health outcomes, and safety limits.
Content last updated . This page has not been medically reviewed.
The question
Does it matter whether a vitamin D supplement or fortified food contains D2 or D3? Vitamin D is mainly found in two forms, D3 (cholecalciferol) and D2 (ergocalciferol), and fortified foods can contain either. [1] Trials that compared the two directly found that D3 raised the blood marker of vitamin D status more than D2. Whether that changes health outcomes is much less certain, and no form is the right choice for everyone. For roles, food sources and deficiency, see Vitamin D.Evidence labels used on this page: established nutritional role (vitamin D is needed for bone health), evidence in adequately nourished people, mixed, insufficient evidence, indirect (each form tested against placebo, not against the other).
The two options side by side
| Option | What it is | What is documented | Evidence strength | Caution |
|---|---|---|---|---|
| D2 (ergocalciferol) | One of the two main forms of vitamin D. [1] | Raised blood 25(OH)D less than D3 in pooled trials in adults. [2][3] | Biomarker only | A lower blood number is not proof of a worse health result. |
| D3 (cholecalciferol) | The other main form. [1] | Raised blood 25(OH)D more in pooled trials, including daily-dose trials. [3] | Biomarker only | The same total-amount limits apply as for D2. |
What the comparison trials found
| Question | What the source found | Strength of evidence |
|---|---|---|
| Which form raises blood 25(OH)D more? | A 2012 meta-analysis of randomized trials in adults concluded D3 is more efficacious at raising serum 25(OH)D than D2. [2] | Biomarker, adults |
| Does daily dosing change that? | In that analysis the advantage appeared with single large (bolus) doses, but "the effect was lost with daily supplementation." [2] | Biomarker |
| Is the gap still there with daily dosing? | A 2024 meta-analysis of 20 comparative studies found D3 still raised total 25(OH)D more; the D2 group was about 10.39 nmol/L (40%) lower in the daily-dose comparisons. [3] | Biomarker, adults |
| Does body weight matter? | In that 2024 analysis the D2 versus D3 difference lost significance mainly in people with a BMI above 25 kg/m2, though BMI data were available for only 13 of 17 daily-dose comparisons. [3] | Biomarker, subgroup |
| Does the form change death rates? | A Cochrane review found D3 seemed to decrease mortality in elderly people living independently or in care, while D2 had no statistically significant beneficial effect. [4] | Mixed and indirect |
Official amounts (UK, NHS)
Amounts are not form-specific. The NHS says children from the age of 1 year and adults need 10 micrograms (400 IU) of vitamin D a day, including pregnant and breastfeeding women. [5] The NHS gives 10 micrograms as equal to 400 IU. [5] It also says not to take more than 100 micrograms (4,000 IU) a day, because it could be harmful. [5] Other countries set different figures. We could not read the US NIH Office of Dietary Supplements page (access was blocked), so we do not quote US figures here; see RDA, AI, DV and UL.No universal winner
D3 has the stronger blood-marker data, and D2 has not been shown to be worse for health outcomes in head-to-head trials. Which form suits a person depends on blood level, total amount, body size, diet and clinician advice, none of which this page can assess.Frequently asked questions
Is vitamin D3 better than D2?
For raising the blood marker 25(OH)D, trials favor D3, although the size of the difference depends on dosing pattern and possibly body weight. [2][3] Whether that translates into better health outcomes has not been shown in direct comparisons.
Is D2 safe?
Both forms are used in supplements and fortified foods. [1] Safety depends mostly on total amount, which is why upper limits such as the NHS 100 microgram (4,000 IU) daily figure apply to vitamin D overall. [5]
Can I switch from D2 to D3?
That is a question for whoever prescribed or advised your supplement, especially if you take a high prescribed amount or have a condition affecting calcium.
Is D3 vegan?
Proper evidence not found in our sources for how each product is made. Check the label and ask the maker.
Does the form matter for children or pregnancy?
Proper evidence not found in the sources we read for a D2 versus D3 comparison in children or pregnancy. The NHS gives amounts for these groups as amounts of vitamin D. [5] Ask a clinician.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read this
- 25(OH)D is a blood marker, not a health outcome. A higher number does not by itself mean fewer fractures or illnesses. [2]
- The mortality finding is indirect. The Cochrane trials compared vitamin D with placebo or no intervention, not D2 with D3, and the review points to attrition bias from participant dropout. [4] It cannot say D3 is better for survival.
- Proper evidence not found for head-to-head trials of D2 versus D3 measuring fractures, falls or infections in adequately nourished adults. We searched the reviews above (PubMed records read on 2026-10-23) and did not find them.
- Proper evidence not found in the sources we read on how each product is made, so we cannot say whether a given D3 product suits a vegan diet. Check the label and the maker; see Supplements in vegetarian and vegan diets.
Safety and who should ask a clinician
- Too much. Taking too many vitamin D supplements over a long period can cause calcium to build up in the body (hypercalcaemia), which can weaken the bones and damage the kidneys and the heart. [5] People with kidney problems should ask a clinician first.
- Pregnancy, breastfeeding and children. For children the NHS says not more than 50 micrograms (2,000 IU) a day at ages 1 to 10, and not more than 25 micrograms (1,000 IU) a day for infants under 12 months. [5] A clinician decides what is right for an infant or a pregnancy; see Pregnancy and breastfeeding.
- Prescribed vitamin D. If a clinician has prescribed a specific form and amount, that is a decision for them. Do not swap forms alone.
- Duplicates and medicines. Vitamin D appears in multivitamins and calcium products; see Amounts and duplicate ingredients and How interactions work. A pharmacist can check your medicines.
- Before surgery. Tell the surgical team about every supplement: Supplements before surgery.
- Testing. For what blood tests do and do not show, see Vitamin D deficiency and testing.
References
- Sources of vitamin D for humans. Int J Vitam Nutr Res, 2022 Read 2026-10-23.
- 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 Read 2026-10-23.
- Comparison of the Effect of Daily Vitamin D2 and Vitamin D3 Supplementation on Serum 25-Hydroxyvitamin D Concentration: A Systematic Review and Meta-Analysis. Adv Nutr, 2024 Read 2026-10-23.
- Vitamin D supplementation for prevention of mortality in adults. Cochrane Database Syst Rev, 2014 Read 2026-10-23.
- NHS, Vitamin D (UK). Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.