This guy says the same thing about retinol (vitamin A supplements), but also says vitamin D3 is safe http://www.vitamindcouncil.org/news-archive/2008/proper-vitamin-dvitamin-a-ratio/
I don’t think there’s an established ideal ratio and vitamin K is involved in the balance too, so it is pretty complicated. There’s a lot of info in this article http://www.westonaprice.org/blogs/2010/12/16/is-vitamin-d-safe-still-depends-on-vitamins-a-and-k-testimonials-and-a-human-study/
I think I was taking way too much at one point because I was having 2 cod liver oil caps and a separate vitamin A supplement. It’s worth doing a bit of background reading to avoid silly mistakes like that. If you don’t want to take retinol, you could try eating beef/lamb liver once a week and lots of veggies. Liver contains a lot of other good nutrients too. It’s kind of like a “supplement” food.