Everything I have read says rabbits are the same as us in that they can store vitamin D for later use, so I would say no. Plus some pellets have vitamin D in them (though supplements are never as good as the natural source).

You might be thinking of a particular type of Vitamin D (Vitamin D3). Anyway, it’s what an animals body will create naturally when exposed to sunlight, and so many House Rabbits may lack in that, but some pellets, like Oxbow add that particular vitamin in. So check your pellets and see if Vitamin D3 is included. If it is, then you probably are just fine. And honestly, I don’t know what the consequences are of having that be lacking (I know what it can be for humans and so I would assume the same would be for other animals) — I have read a little bit about it, but I definitely need to take the time to research this part a bit more so I can offer decent advice for rabbit care on the matter.

Jack was on pelletless diet so he did not get his Vit D3 from pellets, but he also loved sitting in a window lounge box where he could get some morning sun in one corner. Not sure though if Vitamin D (via the sun) can make