There is the option of being tested for polymorphisms of 1-2 of the most relevant metabolic enzymes, which account for some of the bleeding risk. My impression is that genotyping is not routinely done. Also, warfarin is risky in normal metabolizers (many many drug/food/disease interactions). I agree with Richard on the overall cost-benefit. (ETA: Though there are new expensive drugs approved for some of the same indications -- rivaroxaban and dabigatran -- that show some promise of being safer.)