For the passed few weeks my INR is low and then the following week it’s high .Have been in the range 1.6 to 3.4 I do understand how frustrating it is My hematologist just up my warfarin a few mg up .Have been on Heprin injections but now I’m only increasing the warfarin.I worried every Monday morning why. I have to test .I believe we’re either going over our points of 10 or the meter is not functioning correctly.Well ,just monitor your intake of your mcg foods in Vitamins K.Good luck Tuesday .