@ysmina-- There is a type of cod liver oil called "fermented cod liver oil" and it's supposed to be the best type out there. I've heard that it's safer and more beneficial.
I think that fish oil supplements or cod liver oil supplements can be taken for Omega 3 but they're not all created equal. I have used both supplements in the past but I made sure that the supplement was purified and up to standards.
So as long as you get a high quality supplement, you don't need to worry. But ask your doctor about it to make sure that it's safe for you.