Is it possible side effect of coumadin (warfarin)?

Bleeding: If not monitored carefully, Coumadin (warfarin) may Prohibit proper clotting of blood, causing easy bruisability and bleeding.

Bruising: Any side effect of Coumadin (warfarin) would be related to bleeding, as dr. Lau said. You might get bruising, which is bleeding under or into the skin. You can get a nose bleed or gum bleeding when you brush your teeth. You could have blood in your stool or your urine. You can even develop pain and swelling due to an accumulation of a lot of blood in a small space, but these are all from bleeding.

Depends: It varies and depends on the side effect. It's hard to say: some side effects are major ... Others are minor and if tolerable are okay. If bleeding, allergic reactions, falls happen, then these are major and it needs to be stopped.