Vitamin D2 vs. Vitamin D3: What's the Difference?

If you’re searching for the perfect vitamin D supplement, then you may have a few questions: What is the difference between vitamin D and D3? How does D2 compare? Which is the most effective type of vitamin D?
Before we weigh in on vitamin D vs. D3 and the other questions, here’s a quick refresher on vitamin D and the important role it plays in human health:
Known as “the sunshine vitamin,” vitamin D is an essential nutrient that supports bone and muscle structure, immune function, cardiovascular health, hormone balance, healthy skin, good mood, and more.
But unlike many other essential nutrients, few foods naturally contain vitamin D – eggs, certain types of fish, and mushrooms. Several foods are also fortified with vitamin D, including orange juice, milk, yogurt, nut milks, and cereals.
That's where the sun comes in; most of our natural daily vitamin D comes from direct exposure to the sun’s UV rays. However, some factors can limit this, including geographical location, season, a lack of time outdoors, skin pigmentation, and more. For these reasons, many people choose to take a vitamin D supplement year-round or during certain seasons.
Types of vitamin D
Now, back to the question that got you here – what is the difference between vitamin D and D3?
There are two main types of vitamin D – D2 and D3. So, although you may have originally been searching for vitamin D vs. D3, the real comparison is vitamin D2 vs. vitamin D3 – because vitamin D3 is vitamin D, or one form of vitamin D.
One of the key differences between the two types is their natural sources; vitamin D2 is primarily found in plants – mushrooms is a primary source along with fortified foods. Vitamin D3 is exclusively found in animals – the highest source being wild caught salmon, which contains 600-1,000 IU in a 3.5-ounce serving.
However, D3 is the type your skin produces when exposed to natural sunlight. When this happens, it triggers a chemical reaction and your body begins to turn that glorious sunshine into vitamin D.
Vitamin D2 vs. D3: What the research says
So, which form of vitamin D is best? Several research studies show that while both D2 and D3 can raise your vitamin D level, D3 is king due to its effectiveness, efficacy, and overall potency.
A 2022 retrospective observational cohort study compared the effectiveness of D2 to D3 in raising serum vitamin D levels. Researchers compared four groups: vitamin D2 injection, vitamin D3 injection, a combination of vitamin D2 injection + D2 tablet, and a combination of vitamin D3 injection + D2 tablet.
While all had a statistically significant effect on raising serum concentration, the vitamin D3 injection group was twice as effective as D2, raising it by a mean of 6.1 ng/mL compared to 3.2 ng/mL.1
A recent meta-analysis of 20 comparative studies on daily dosing had similar findings; vitamin D3 led to a greater increase than D2, although both were effective at raising levels.2
Finally, a 2004 study compared the effects of D2 and D3 in 20 healthy male participants over 28 days. Vitamin D initially increased at about the same rate for both groups during the first three days, but by 14 days, D2 fell to baseline while D3 peaked.3
In their calculations, the authors reported that D2’s potency was less than a third of D3’s, and they cautioned physicians about vitamin D2’s “markedly lower potency and shorter duration of action relative to vitamin D3.”
Thorne’s vitamin D3 suite
Depending on your unique health needs, Thorne’s vitamin D products – all formulated with vitamin D3 – come in a variety of dosages and formats.
Consider Thorne’s vitamin D capsules, a best-selling lineup available in several dosages: Vitamin D-1,000, Vitamin D-5,000 (an NSF Certified for Sport® product), and Vitamin D-10,000. For an easy-to-mix option, check out Thorne’s Vitamin D Liquid.
To assess your baseline level of vitamin D, try Thorne’s Vitamin D Test. This at-home blood test measures total vitamin D and provides a personalized plan with diet and supplement recommendations.
References
- Alayed Albarri EM, Sameer Alnuaimi A, Abdelghani D. Effectiveness of vitamin D2 compared with vitamin D3 replacement therapy in a primary healthcare setting: a retrospective cohort study. Qatar Med J. 2022;2022(3):29. doi:10.5339/qmj.2022.35
- van den Heuvel EG, Lips P, Schoonmade LJ, et al. 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;15(1):100133. doi:10.1016/j.advnut.2023.09.016
- Armas LA, Hollis BW, Heaney RP. Vitamin D2 is much less effective than vitamin D3 in humans. J Clin Endocrinol Metab. 2004;89(11):5387-5391. doi:10.1210/jc.2004-0360