Vitamin D and D3: What's the Difference?

The difference between vitamin D and D3 is mostly a matter of naming. "Vitamin D" is the family name for two main forms: vitamin D2 (ergocalciferol), which comes from plant and fungal sources, and vitamin D3 (cholecalciferol), the form your skin makes in sunlight and the form found in most animal foods.^[1] So when people ask whether vitamin D is the same as D3, the answer is that D3 is one type of vitamin D. Many people choose a D3 supplement such as Orzax Vitamin D3 2,000 IU softgels because research suggests D3 raises blood vitamin D levels more than D2 does.^[1][2]

Below, we explain how D2 and D3 differ, what the studies found, and how to read a vitamin D label with confidence.

Is vitamin D the same as D3?

Not exactly. Vitamin D is the umbrella term, and D3 is one member of the group. When a food label or lab report says "vitamin D," it could refer to D2, D3, or both added together.^[1]

Vitamin D is a family, not a single compound

Both D2 and D3 are fat-soluble compounds that the body handles in a similar way. The main structural difference is in their side chains, which is why they come from different starting materials:

• Vitamin D2 (ergocalciferol) is made from ergosterol, a sterol found in fungi such as yeast and mushrooms.^[1][4]
• Vitamin D3 (cholecalciferol) forms from 7-dehydrocholesterol, a compound in human and animal skin, when it is exposed to UVB light.^[1]

How your body processes both forms

Neither form is active when you first swallow it or make it in your skin. Your liver first converts vitamin D into 25-hydroxyvitamin D, or 25(OH)D, also called calcidiol. Your kidneys then convert 25(OH)D into 1,25-dihydroxyvitamin D, or calcitriol, the active form.^[1][4]

That active form works by binding to the vitamin D receptor in cells throughout the body.^[4] Blood 25(OH)D is the marker your clinician measures to check your vitamin D status, and its half-life is about 15 days.^[1]

The difference between vitamin D2 and D3

Both forms end up on the same metabolic pathway, but they differ in where they come from and how they show up on store shelves. Here is a side-by-side summary.

Feature	Vitamin D2 (ergocalciferol)	Vitamin D3 (cholecalciferol)
Natural source	UV-exposed fungi, including mushrooms	Human skin exposed to UVB; animal foods
How supplements are made	UV irradiation of ergosterol from yeast	UV irradiation of 7-dehydrocholesterol from lanolin (sheep's wool), or animal-free D3 from lichen
Common food examples	UV-exposed mushrooms	Fatty fish, egg yolks, most fortified milk
Effect on blood 25(OH)D	Raises it	Raises it more, and keeps it elevated longer, in most studies
Active form in the body	Converted to calcitriol	Converted to calcitriol

Sources for the table: NIH Office of Dietary Supplements,^[1] Bikle,^[4] and Cardwell and colleagues.^[5]

Where vitamin D2 comes from

Mushrooms are the classic D2 food. When they are exposed to UV light, they can produce nutritionally meaningful amounts of vitamin D2.^[5] A review of mushrooms as a vitamin D source noted that D2 is the most common form in mushrooms, while D3 is the most common form in animal foods.^[5]

The same review described UV-exposed mushrooms as possibly the only non-animal, unfortified food that can provide a substantial amount of vitamin D2 in a single serving.^[5] Commercially, D2 for supplements is made by exposing ergosterol from yeast to UV light.^[1]

Where vitamin D3 comes from

Your skin makes D3 when UVB light reaches it, which is why vitamin D is often called the sunshine vitamin. In supplements, D3 is typically produced from lanolin, the natural oil in sheep's wool.^[1]

If you follow a vegan diet, note that lanolin-derived D3 is not vegan. An animal-free D3 sourced from lichen is also available, so check the label or ask the manufacturer about the source.^[1]

What research shows about D2 and D3

Both forms raise blood 25(OH)D. The real question researchers have asked is which one raises it more, and by how much. Most of the evidence points toward D3, with some important nuances.^[1]

Meta-analyses comparing the two forms

A 2012 systematic review and meta-analysis of randomized controlled trials concluded that vitamin D3 is more efficacious at raising serum 25(OH)D than vitamin D2.^[2] The authors noted that more research is still needed on how the two forms are metabolized and whether results differ by age, sex, and ethnicity.

A 2021 meta-analysis pooled 24 studies with 1,277 apparently healthy participants. D3 raised total 25(OH)D by an average of 15.69 nmol/L more than D2 (95% CI 9.46 to 21.93), and it also lowered parathyroid hormone more consistently.^[3] The authors reported the advantage held regardless of participant demographics, dose, or vehicle.

Large single doses and daily doses

Dosing schedule seems to matter. In the 2012 meta-analysis, D3 had a significant advantage when given as a large bolus dose, but that effect was lost with daily supplementation.^[2] The 2021 analysis similarly found smaller differences between the forms at lower doses.^[3]

One randomized, double-blind trial gave healthy adults aged 18 to 84 either 1,000 IU of D2, 1,000 IU of D3, or 500 IU of each daily for 11 weeks at the end of winter.^[6] Average 25(OH)D rose from 16.9 to 26.8 ng/mL in the D2 group and from 19.6 to 28.9 ng/mL in the D3 group, and the authors concluded the two were equally effective at that dose.^[6]

D2 may lower D3 levels

An 8-week randomized trial in Helsinki followed 33 healthy women aged 20 to 37 during late winter. Daily 25 mcg (1,000 IU) supplements of either D2 or D3 both raised total 25(OH)D compared with placebo.^[7]

However, D2 supplementation lowered blood 25(OH)D3, and the authors described D2 as less potent than D3 for raising total 25(OH)D. D2 added to bread made from UV-irradiated yeast did not raise total 25(OH)D at all in this study.^[7]

Vitamin D and D3 in foods and labels

Few foods are naturally rich in vitamin D, which is one reason fortified foods and supplements play such a large role in the US.^[1]

Food sources and their forms

These per-serving values come from the NIH Office of Dietary Supplements:^[1]

• Farmed rainbow trout, 3 oz cooked: 645 IU (D3)
• Sockeye salmon, 3 oz cooked: 570 IU (D3)
• UV-exposed white mushrooms, ½ cup raw: 366 IU (D2)
• Fortified 2% milk, 1 cup: 120 IU (usually D3)
• Egg yolk, 1 large: 44 IU (D3)

For context, the RDA is 600 IU a day for ages 1 to 70 and 800 IU for adults over 70.^[1] If you want to know how sunlight and seasons change the picture, our guide to vitamin D in fall and winter covers it in detail.

Reading IU and mcg on a label

US labels may list vitamin D in micrograms (mcg), International Units (IU), or both. The conversion is simple: 1 mcg equals 40 IU.^[1]

• 10 mcg = 400 IU
• 15 mcg = 600 IU
• 50 mcg = 2,000 IU
• 100 mcg = 4,000 IU (the adult upper limit)

Look for the word "cholecalciferol" or "ergocalciferol" in the ingredient list to see which form you're getting. Our guide on how to read supplement labels walks through the rest of the panel.

How to choose and take a vitamin D3 supplement

Whichever form you choose, a few practical steps help you get the most from it:

1. Check the form. If your goal is to raise or maintain blood 25(OH)D, research generally favors D3.^[2][3]
2. Check the source if diet matters. Lanolin-derived D3 is animal-based; lichen-derived D3 is animal-free.^[1]
3. Add up all sources. Count multivitamins, fortified foods, and combination products so your total stays within the upper limit.^[1]
4. Take it with a meal that includes fat. In a trial of 50 healthy older adults given a single 50,000 IU dose of D3, peak plasma vitamin D3 was 32% higher when taken with a fat-containing meal than with a fat-free meal.^[8]
5. Ask about testing. A 25(OH)D blood test is the standard way to check your status.^[1]

How Orzax Vitamin D3 fits

Orzax Vitamin D3 uses cholecalciferol, the D3 form. Orzax Vitamin D3 2,000 IU comes in small softgels with no artificial colors, preservatives, sweeteners, or flavors. A 2,000 IU (50 mcg) serving stays within the 4,000 IU adult upper limit.^[1] Vitamin D supports normal immune function and helps maintain healthy bones and muscles.*

Orzax also offers Vitamin D3 10,000 IU softgels, which are for use under a healthcare provider's guidance, since that amount exceeds the adult upper limit.

If you'd like a daily routine that pairs D3 with black seed oil, the Daily Immune Support Duo combines Vitamin D3 2,000 IU softgels with Black Seed Oil Liquid (5,000 mg cold-pressed black seed oil per 1 tsp serving, standardized for thymoquinone). Our black seed oil benefits guide covers what research says about that oil.

Safety: who should talk to a clinician first

Vitamin D is fat-soluble, so excess amounts can build up. Toxicity almost always comes from taking too much in supplement form, not from sun or food.^[1]

• Upper limit: 4,000 IU (100 mcg) a day for teens and adults from all sources, unless your clinician recommends more. Children have lower limits.^[1]
• Signs of too much: very high intakes can raise blood calcium, which may cause nausea, vomiting, muscle weakness, excessive thirst, and kidney stones.^[1]
• Blood levels: 25(OH)D above 50 ng/mL (125 nmol/L) is associated with potential adverse effects.^[1]
• Medications: orlistat can reduce vitamin D absorption, and statins, steroids, and thiazide diuretics may interact with vitamin D. Review your supplements with your prescriber.^[1]
• Pregnancy and nursing: the RDA is 600 IU and the UL is 4,000 IU. Talk with your provider before starting any supplement.^[1]
• Health conditions: if you have kidney or liver concerns, high calcium levels, or a condition that affects fat absorption, get personalized advice first.

Frequently Asked Questions

Is vitamin D the same as D3?

D3 is one form of vitamin D. "Vitamin D" is the general name that also includes D2, so a product labeled simply "vitamin D" could contain either form.^[1]

Which is better, vitamin D or D3?

Since D3 is a type of vitamin D, the more useful question is D2 or D3. Most research, including two meta-analyses, found D3 raised blood 25(OH)D more effectively, especially at higher or less frequent doses.^[2][3]

What is the difference between D2 and D3?

D2 comes from ergosterol in yeast and mushrooms, while D3 forms in skin and is found in animal foods, lanolin, and lichen. Both are converted to the same active form in the body.^[1][4]

Can you take vitamin D2 and D3 together?

One 11-week trial included a group that took 500 IU of each daily, and their 25(OH)D rose similarly to the single-form groups.^[6] If you combine products, count both forms toward your daily total and stay within the upper limit.^[1]

Is vitamin D3 vegan?

Not always. Most D3 is made from sheep's wool lanolin, but animal-free D3 from lichen is available.^[1] Check the label for the source.

References

1. National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. NIH ODS
2. Tripkovic L, Lambert H, Hart K, 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. PubMed
3. Balachandar R, Pullakhandam R, Kulkarni B, Sachdev HS. Relative efficacy of vitamin D2 and vitamin D3 in improving vitamin D status: systematic review and meta-analysis. Nutrients. 2021;13(10):3328. PubMed
4. Bikle DD. Vitamin D metabolism, mechanism of action, and clinical applications. Chem Biol. 2014;21(3):319-329. PubMed
5. Cardwell G, Bornman JF, James AP, Black LJ. A review of mushrooms as a potential source of dietary vitamin D. Nutrients. 2018;10(10):1498. PubMed
6. Holick MF, Biancuzzo RM, Chen TC, et al. Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D. J Clin Endocrinol Metab. 2008;93(3):677-681. PubMed
7. Itkonen ST, Skaffari E, Saaristo P, et al. Effects of vitamin D2-fortified bread v. supplementation with vitamin D2 or D3 on serum 25-hydroxyvitamin D metabolites: an 8-week randomised-controlled trial in young adult Finnish women. Br J Nutr. 2016;115(7):1232-1239. PubMed
8. Dawson-Hughes B, Harris SS, Lichtenstein AH, Dolnikowski G, Palermo NJ, Rasmussen H. Dietary fat increases vitamin D-3 absorption. J Acad Nutr Diet. 2015;115(2):225-230. PubMed

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for informational purposes only and is not a substitute for professional medical advice. Consult your healthcare provider before starting any supplement, especially if you are pregnant, nursing, taking medication, or have a medical condition.