I''ve been self testing my INR for about a month. I borrowed the machine from the Hughes Foundation and got my strips on prescription. I've managed some successful finger prick tests but 2 out of 3 have shown an error 5 and I'm rapidly running out of strips. It's either not a big enough drop of blood or I'm not applying it to the strip properly or something else? I followed the DVD on using the Coaguchek XS but I'm still wasting loads of strips and I'm concerned my GP won't prescribe me any more right now. These were meant to last at least 6 months. Has anybody got any tips on avoiding error 5? I would be very grateful as I really appreciate the benefits of self testing. Thank you.