Giving Dog Fish Oil. Side effects of fish oil at recommended administration levels, fish oil is very safe in dogs. You can even purchase a supplement from your local pharmacy or drugstore, as long as you make sure that it's not mixed with other ingredients that can harm a pup.

Check the back of the label. Fish oil for dogs and puppies. If your fish oil supplement is pure fish oil, it may be safe to also give to your dog, but you should discuss it with your veterinarian first to be sure.