Can i add cod liver oil with vitamin a & d to my supplements?

Probably: Just use in moderation, and make sure it is purified and not high in mercury and other toxins.

Yes, but...: Cod liver oil is a great source of omega-3 fatty acids as well as vitamins a, d, and e, and is a very helpful supplement in general. All of these are necessary nutrients, but they should be taken in moderation. Both vitamin e and omega-3's can thin the blood and cause easy bleeding, and fat-soluble vitamins (a, d, e, k) can build up to toxic levels if large doses are taken on a regular basis.