Greetings. Thank you for your question and welcome to HCM. I understand your concern. Yes, this is everyone s problem, both for patients and for us, doctors. Oral anticoagulants, such as acenocoumarol, interact not only with other medication in the treatment regimen, but also with certain food and meteorological changes. On the other hand, the other delicate problem is that the international normalized ratio (INR) s target window is very narrow (2.5-3.5 in case of post-mitral valve replacement). Plus, the other problem is that acenocoumarol will only take effect 48 hours after starting, and the INR you get in your hand, actually reflects the dosage taken two days before. In our clinic s experience, we use the hospitalization period to adjust the right dosage by measuring INR once in two days, and be safer with the dosage when we discharge the patient. Every time that there is a disturbance in the standard dosage, we then measure INR every three-to-five days to readjust the dosage. I know this costs, but the reality is that we are in very narrow borders that separates us from clot formation on one side, and from excessive blood thinning, up to dangerous INR figures sometimes, on the other. I always prefer to adjust the disturbed dosages, by measuring the INR in three-to-five days periods, until a stable dosage is achieved, than taking the risk of leaving the patient without anticoagulation (INR under 2.5) or thinning the blood more than it is needed (INR above 4.0). I hope I was helpful and thorough with my answer. Take care. My regards, Dr. Meriton