I agree with jdrussell.My mother,80 years,has been on Warfarin for 10 years,following an Aortic valve replacement.She has to have her INR checked regularly,so that the dosage of warfarin,can be adjusted if necessary.She goes to have this checked,usually once a week,depending on her previous result.I would suggest that once a month is too long,but I would like to think that a blood test could be performed in Turkey on a regular basis,as my mother has to constantly change her dosage of warfarin.I hope this helps you.