Reviewed By Dr Mark Watson
A lot of places list vitamin D3 specifically on a label, but you’ll rarely if ever see any other form of vitamin D listed specifically which can lead many people to wonder what exactly the difference is between the two specifications. And the answer is sometimes nothing, sometimes something that will be important to vegetarians and vegans.
The short answer is that all types of Vitamin D are as you would assume D vitamins. The human body can only process vitamin D2 and D3 and these are the ones you’ll find in supplements.
So what’s the difference between vitamin d3 and vitamin d?
- Vitamin D3 is the form that the human body makes from sunlight and as such this is what we find in animals that produce it in the same way, meaning it comes mostly from animal products (particularly fish oils, organs and eggs).
- Vitamin D2 mostly comes from plants, although most don’t have a huge amount with the exception of mushrooms. It’s also a lot less expensive and thus found more commonly in vitamins.
- Most studies show that they’re equally bioavailable and there isn’t much difference in supplementing the two if any at all. 
- Vitamin D2 is usually not sold in particularly high doses over the counter.
In short the main difference between the two is the source of the product and really it only matters if you’re a vegan or vegetarian looking to avoid animal products.
Is Vitamin D3 Suitable For Vegans?
If you see vitamin d3 on the label and haven’t seen the product marked as suitable then you should check with the manufacturer and ask them if their vitamin d3 is suitable for vegetarians. If it’s from egg yolks it could be fine, but in other cases it won’t be. As for vegans it’s unlikely that vitamin d3 will be suitable for vegans.
Why is vitamin d3 sold in higher doses and preferred in a lot of premium supplements?
It was previously believed that d3 was safer although the upper limit for vitamin d supplementation is generally considered to be 4000 iu per day, meaning it is well beyond what most people would supplement either way. 
1 - https://www.health.harvard.edu/newsletter_article/vitamin-d2-or-d3
2 - https://www.health.harvard.edu/staying-healthy/taking-too-much-vitamin-d-can-cloud-its-benefits-and-create-health-risks