What are the side effects of the blood thinner Coumadin?

Coumadin, known generically as warfarin, can cause nausea, abdominal pain or loss of appetite, reports WebMD. More serious side effects include heavy menstrual flow, frequent nosebleeds, prolonged gum bleeding, headache or dizziness. Some people experience an allergic reaction to the drug and might have itching, swelling and trouble breathing.

Coumadin is used to treat blood clots by thinning the blood. It also helps prevent new clots from forming. The drug is often prescribed to heart attack patients or patients with an irregular heart rhythm. Coumadin is also prescribed to patients recovering from surgery, reports WebMD. Coumadin is usually taken orally.