A normal INR performed 48 hours after ingestion excludes significant warfarin overdose. In this case, it would suggest that the history is spurious – either a different medication was taken or she did not actually swallow as many tablets as reported. Warfarin increases your risk of severe or fatal bleeding, especially if you have certain medical conditions, if you are 65 or older, or if you have had a stroke, or bleeding in your stomach or intestines. So - What happens if you overdose on warfarin (coumadin) (Its an anti-coagulant)? I know tripling a dose would possibly lead to vessels breaking under your skin (is on the pharmacy label), but what would happen if someone took perhaps 100 times their dose? The instructions with most drugs, including Warfarin say that you should never double up if you miss a dose, just carry on as normal. The absorption time of Warfarin is about 4 hours and the half life is 40 hours, so you would expect it to be MUCH less tolerant of an overdose than a missed dose. you would be a walking time bomb.you could have a bleed in your brain and have a stroke, or have a bleed in your stomach and start vomiting blood, or have a bleed deep in your belly and cause other problems, or have a bleed in your joint that causes a very painful swollen joint. You do know that warfarin is the main ingredient in many rat poisons, don't you? We use its anticoagulant properties in a very careful manner and in a fairly precise dosage. PRECAUTIONS: Before taking warfarin, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. The antidote for a warfarin overdose is vitamin K, which can be given in tablet or injectable form. These treatments must be done carefully. If too much vitamin K is given, this can reverse the effect of warfarin so much that it is no longer effective for preventing blood clots. Are you aware that one of the main ingredients in rat poison is Warfarin? Are you also aware that it's prescribed for humans as a blood thinner? The most important effect of a Coumadin overdose is bleeding. This can include obvious bleeding, such as vomiting of blood, nosebleeds, or bright red blood in the stool, or bleeding that is less obvious, such as internal bleeding.