What are the risks of having too high levels of coumadin (warfarin)?

The dose that works.: There is no exact upper limit to Coumadin (warfarin) although the most I have seen someone need is about 12mg daily. Because Coumadin (warfarin) is so closely monitored with blood tests the right answer is the limit is the dose that gets you to your goal inr. Some people are genetically "coumadin resistant" and need much higher doses and people with high vitamin k diets also need higher doses.