I am 56 years old and have been on warfarin now for 16 months. I am expecting to be on it the rest of my life. My INR has kept quite stable in that time until recently when I was put on a course of antibiotics which upset it all. I went from a INR test every ten weeks to a test every week. I find it difficult to get to the doctors during surgery hours so this has been a bit of a problem. I have in mind to buy a Coaguchek XS self testing machine so I can do this at home and email the result to the surgery. Has anyone had experience of these machines and have you come across any problems with home testing.