Thanks Bluetit. What needed calibration was the lancing device which failed to reveal any blood to start with. The first attempt (with blood!) produced a figure of 5.8, but I thought I'd test again for consistency. Once again couldn't get enough blood onto the strip and wasted that one. The next was a rather clumsy effort with more blood on the underside and a reading of 4.2. I finally did what I consider a perfect procedure and got 5.2. This is with my breakfast getting cold in the kitchen and not having eaten since the evening before, some 15 hours previously (late Saturday breakfast. Treated myself to two sausages and some mushrooms so very little carbs but will test myself again in an hour and a half as seems to be the recommended interval.