When comparing vitamin D2 vs D3, picking up two distinct bottles of vitamin D at the pharmacy can be confusing because they may look similar but contain different forms of the vitamin. One will be labeled “vitamin D3,” while the other will be “vitamin D2.” Both are forms of vitamin D, but why are they different, and does one work better than the other?
The short version: Both are legitimate ways of getting vitamin D; however, they come from different sources, undergo different biological processes within the body, and according to scientific literature, do not seem to be equally effective in increasing your vitamin D levels in the blood.
The following article will give you an insight into the science behind it and tell you which one might be a better choice for you.
Vitamin D2 vs. D3 at a Glance
| Feature | Vitamin D2 | Vitamin D3 |
|---|---|---|
| Scientific name | Ergocalciferol | Cholecalciferol |
| Common sources | Fungi (mushrooms exposed to UV light), fortified foods | Animal-derived sources, skin synthesis from sunlight |
| Found in supplements? | Yes | Yes — more common in OTC supplements |
| Raises vitamin D levels? | Yes | Yes |
| Effectiveness at raising 25(OH)D | Effective, but multiple meta-analyses show a smaller and less durable rise than D3 | Effective, with a generally larger and more sustained rise across most studies |
| Vegan availability | Naturally vegan | Traditional D3 is not vegan (lanolin-derived); vegan D3 from lichen is available but less common |
| Common U.S. uses | Food fortification, some prescription-strength formulations | Standard OTC supplementation, food fortification |
What Is Vitamin D2?
Ergocalciferol, or vitamin D2, is derived from plants and fungi; specifically mushrooms that have been irradiated with UV rays. It is also used in food fortification and as supplements in addition to some prescription-strength medications.
Upon ingestion, vitamin D2 gets metabolized in the liver into 25-hydroxyvitamin D2, and then in the kidneys into an active hormone that your body requires. The structure of the metabolic pathway for vitamin D2 activation resembles the one for vitamin D3, however, there are small differences between intermediary products because of which the actions of the two types in the blood differ.
What Is Vitamin D3?
Vitamin D3, or cholecalciferol, is the natural form produced by your own skin on exposure to UVB rays of sunlight. Vitamin D3 is also present in natural animal food products, fatty fish, egg yolk, and certain fortified milk products, and is the most common form available in over-the-counter vitamin D preparations in the United States.
Similar to vitamin D2, it requires two steps for its metabolism. The first step occurs in the liver to convert vitamin D3 into 25-hydroxyvitamin D3, and the second step takes place in the kidney to convert it into calcitriol. Since vitamin D3 is the natural form of vitamin D, there is an argument that it is metabolized slightly better and this idea is supported by the following clinical data.
What Is the Main Difference Between Vitamin D2 and D3?
The two forms differ in a few concrete ways:
- Chemical structure: D2 and D3 differ in their side-chain structure, which affects how efficiently your body’s vitamin D-binding protein transports them and how quickly each is metabolized.
- Source: D2 is plant/fungal; D3 is animal-derived or produced by your own skin.
- Effect on blood 25(OH)D levels: this is where the research shows the most consistent difference D3 generally raises and sustains blood levels more effectively (see the evidence section below).
- Duration: some research suggests D3’s effect on blood levels persists longer between doses than D2’s, though this varies by dosing frequency and study.
- Supplement availability: D3 dominates the U.S. OTC market; D2 is more often used in fortified foods and specific prescription contexts.
Is Vitamin D3 Better Than D2? What the Evidence Actually Shows
This is the most researched question in the D2-vs-D3 debate, and the evidence has accumulated meaningfully over time which is worth walking through rather than just stating a conclusion.
The foundational study: A 2012 systematic review and meta-analysis in the American Journal of Clinical Nutrition (Tripkovic et al.) pooled randomized controlled trials directly comparing D2 and D3. It found that D3 supplementation had a significantly greater effect on raising serum 25(OH)D than D2 overall but with an important nuance: when the researchers separated results by dosing frequency, the D3 advantage was clearly significant for large, infrequent “bolus” doses, while the difference largely disappeared in studies using daily dosing. In other words, the original analysis suggested that for typical daily supplement use, D2 and D3 might perform more similarly than headlines implied.
More recent evidence has shifted this picture. A 2020 meta-regression of nine RCTs found that vitamin D supplementation was effective regardless of form, but the effect size for D3 (standardized mean difference of 1.52) was larger than for D2 (1.16). A more recent 2024 meta-analysis specifically re-examining daily and frequently dosed comparisons found that D3 outperformed D2 even with daily dosing with D2 producing a weighted mean difference roughly 10 nmol/L lower in total 25(OH)D than D3 across the daily-dosing comparisons analyzed.
That same study identified body mass index as a significant factor: the D3 advantage over D2 lost statistical significance in participants with a BMI over 25, suggesting the size of the difference may not be uniform across all body types.
What this means in plain language: The earlier, more cautious conclusion that D2 and D3 perform similarly with daily dosing has been partly revised by newer research showing a more consistent D3 advantage, even with daily dosing, in most populations studied. This is a genuine example of evidence evolving over time rather than being static, and it’s worth being transparent about rather than picking whichever older or newer study best supports a simple headline.
What the evidence does not establish: that a higher blood 25(OH)D level from D3 versus D2 translates into a meaningfully different clinical health outcome (bone density, infection risk, mortality, etc.) for a typical supplement user. Most of this research measures blood levels as the outcome, not downstream health effects an important distinction, since a higher lab number isn’t automatically the same as a better health outcome.
D2 vs. D3 for Vitamin D Deficiency
These two types are applied therapeutically for the treatment of vitamin D deficiency, but in practice the decision is dependent more on availability, prescription, and patient characteristics rather than any general principle.
- Prescription-strength vitamin D2 (usually 50,000 IU capsules) has been a standard treatment in many cases and an option covered by medical insurance, and some doctors still prescribe it for therapeutic courses of vitamin D.
- Vitamin D3 in OTC dosage is the more common option for both maintenance and correction of vitamin D deficiency when taken in proper doses.
- The appropriate type, dosage, and course length for correcting a deficiency should be decided by a doctor based on your lab tests and medical history, not a comparison from a blog post. In case you are not sure about your vitamin D status, read [signs of vitamin D deficiency].
Is Vitamin D3 Better for Everyday Supplementation?
For most people shopping for an everyday, over-the-counter vitamin D supplement without a specific prescription, D3 has practical advantages worth knowing about:
- Availability: it’s the dominant form on U.S. shelves, making it easier to find at a range of doses and formats
- Evidence base: as detailed above, more recent research generally favors D3 for raising and maintaining blood levels
- Format variety: softgels, liquid drops, gummies, and tablets are all widely available in D3
That said, “generally favored by the evidence” isn’t the same as “the only reasonable choice.” Your decision should also weigh dose, product form, dietary preferences, third-party testing, and cost all covered in more depth in our [vitamin D3 buying guide].
Vitamin D2 vs. D3 for Vegans
This is one of the more practical, frequently overlooked differences between the two forms.
- Traditional D3 is most commonly derived from lanolin, a wax obtained from sheep’s wool not vegan, even though it’s an animal byproduct rather than animal flesh.
- Vegan D3 does exist, typically derived from lichen, but it’s less widely available and often costs more.
- D2 is naturally vegan, since it’s derived from fungal sources, making it the more consistently accessible vegan option if a lichen-derived D3 product isn’t available or affordable.
Practical guidance: if you’re vegan, check the label specifically “vitamin D3” alone doesn’t tell you the source. Look for an explicit vegan certification or “lichen-derived” labeling if you want D3 specifically, or choose D2 as a reliably vegan default.
Vitamin D2 vs. D3: Which Should You Take?
D3 may be worth considering if:
- You want a standard over-the-counter supplement for general maintenance
- You want the form more consistently shown to raise and sustain blood 25(OH)D levels in recent research
- Your dietary preferences don’t require a vegan product, or you’re able to find a certified vegan D3 option
D2 may make sense if:
- Your healthcare provider has specifically prescribed or recommended it
- You need a reliably vegan option and don’t want to search for lichen-derived D3
- You’re using a fortified food product where D2 is the form included
For most healthy adults without a specific medical reason to choose otherwise, D3 is the more evidence-supported default for routine supplementation but this isn’t a universal rule, and a provider’s specific recommendation for your situation should take priority over a general guideline.
How Much Vitamin D Do You Need?
This is a separate question from D2 vs. D3 — the form you choose doesn’t change how much you need.
| Age Group | RDA (National Academies of Sciences) |
|---|---|
| 1–70 years | 600 IU (15 mcg)/day |
| 71+ years | 800 IU (20 mcg)/day |
| Pregnant/breastfeeding | 600 IU (15 mcg)/day |
The Tolerable Upper Intake Level for adults is 4,000 IU/day from all combined sources. Clinically prescribed doses for treating a diagnosed deficiency can be substantially higher, but those are supervised, time-limited treatment plans — not a template for ongoing self-directed supplementation.
Can You Take Vitamin D2 and D3 Together?
Generally there is no benefit, to mixing vitamin D2 and vitamin D3 together. Mixing them mainly adds difficulty when you try to keep track of the total vitamin D intake. I have seen people think that taking both forms might be better. The reality is that the total amount of vitamin D still counts toward the same daily upper limit.
If you take a vitamin D2 supplement and also eat foods that are fortified with vitamin D3 or if you take a vitamin D3 supplement and eat vitamin D2‑fortified foods the two forms do not have limits. If you want to combine the forms for a medical reason this is something to discuss with a healthcare provider not something you decide on your own.
What to Look for When Buying Vitamin D
A quick checklist, covered in full detail in our [vitamin D3 buying guide]:
- Confirm which form (D2 or D3) is actually listed on the supplement facts panel
- Check the dose per serving against your actual need
- Confirm vegan status if relevant to you, and don’t assume check the label
- Look for third-party testing (USP, NSF, Informed Choice)
- Review the “other ingredients” for allergens or unnecessary fillers
- Check serving size and calculate cost per serving, not just price per bottle
- Avoid unnecessarily high-dose products marketed for daily use without medical guidance
Myth vs. Fact
| Myth | Fact |
|---|---|
| “D2 doesn’t work — only D3 raises vitamin D levels.” | Both forms raise blood 25(OH)D levels. The evidence suggests D3 tends to do so more effectively and durably, particularly with recent research, but D2 is not ineffective. |
| “D3 is always vegan since it’s ‘natural.'” | Most D3 is lanolin-derived (from sheep’s wool), not vegan. Vegan D3 exists but must be specifically sourced from lichen. |
| “Taking more D2 makes up for its smaller effect compared to D3.” | Simply increasing dose isn’t a substitute for choosing the form your body uses more efficiently, and higher doses of either form still count toward the same upper intake limit. |
| “A higher blood level is always better.” | Evidence for benefit generally applies up to a sufficient range; there’s no established benefit to pushing levels higher than needed, regardless of which form is used to get there. |
Frequently Asked Questions
Vitamin D2 vs. D3: Final Verdict
For people who pick an over-the-counter supplement D3 is usually the better choice. Recent research, including meta-analyses that looked closely at daily dosing shows that D3 raises and keeps blood 25(OH)D levels higher than D2 in most groups studied. So D2 is still a real and effective form of vitamin D. The right choice for you might depend on your diet, any specific medical advice you have and what your healthcare provider recommends for your situation. Neither D3 nor D2 is “healthier” in a sense; the research difference is only, about how well each raises blood vitamin D levels, not about overall health superiority.
Next Steps
- Ready to shop for a D3 supplement? See our [vitamin D3 buying guide] for how to evaluate dose, form, and quality
- Not sure if you actually need supplementation? Start with [signs of vitamin D deficiency] to understand symptoms and testing
- Want the full picture on what vitamin D does in the body? See [vitamin D benefits: what does vitamin D actually do for your body?]
Sources
- 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. American Journal of Clinical Nutrition, 2012.
- Tripkovic L, et al. Follow-up meta-analysis comparing more frequently dosed vitamin D2 and D3, 2024 (PMC10831883).
- Meta-regression of RCTs comparing D2 and D3 supplementation effect sizes on 25(OH)D, 2020 (PMC7259151).
- National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals.
- National Academies of Sciences, Engineering, and Medicine (Food and Nutrition Board). Dietary Reference Intakes for Calcium and Vitamin D.
Disclaimers
Medical disclaimer: This article is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always talk to a qualified healthcare provider before starting any supplement or making treatment decisions for a diagnosed condition.
Editorial transparency: This article was researched and written using current peer-reviewed meta-analyses and NIH/NASEM guidance, as cited above. It has not been reviewed by a licensed medical professional. We have not personally tested any products referenced in related ReliefWellPro content; product evaluations on this site are based on publicly available formulation data, third-party testing information, and published research rather than in-house testing.
Affiliate disclosure: Some links on ReliefWellPro may be affiliate links, meaning we may earn a commission if you make a purchase, at no additional cost to you. This does not affect our editorial evaluation of any product.
