If you are taking blood thinning medications or if you are preparing for surgery, it is necessary to discuss using fish oil or krill oil further with your doctor. As with anything, it is probably wise to stop using it a few weeks prior to elective surgery.
Actually, two things: If you're not allergic to krill oil, it is touted to be the superior form of animal based omega three oil. Second, all people should ideally use krill oil or fish oil everyday indefinitely. If you're able to take the krill oil, use that one. I've learned that fish oil can be rancid without one actually knowing this, whereas, krill oil doesn't have this tendency so much.