Is it safe to take cod liver oil (which contains high amount vit a) with a multivitamin (also containing vit a)?

Depends on the dose: Please be aware that too much of Vitamin supplement does not do any good to your body There might be harmful effect from overusing them I would suggest to stick yourself to one source of supplement.

Vitamin A: Unless you have a lab study indicating that your vitamin a is low I suggest you not use cod liver old unless your doc asked you to. High quality Marine Fish Oil would be a good substitute if you are not on a blood thinner. Please see your doc to coordinate this. Peace and good health.