Curious if anyone else experiences this when calibrating their CGM. When I do the two calibrations for a new sensor on my Dexcom G4, my glucometer readings are frequently 20-30 points apart if I do one stick from each hand. I’m wondering if that causes the CGM’s readings to be less than ideal until I have recalibrated a few more times? Does anyone else notice such a variation when doing finger sticks from each hand?
the meter you use to calibrate the CGM is only +/- 20% accurate in the first place. It is common to get different results from different sticks, as well as different results from the same sticks. An example is if your home meter reads 140, you actual blood sugar can be anywhere between 168 and 112.
the best results I have seen from calibration is when I wait for my blood sugar to be very stable, say 4 hours since my last meal or so. then I know the CGM (which is less accurate than the glucose meter and can lag my bs meter because it measures electro-chemical concentration in interstitial fluid) has caught up to and is as close as possible to actual blood glucose.
Calibrations after insertion is especially tricky because of the trauma associated with sensor insertion and the difficulty in a good reading while your body is trying to heal. depending on your sensitivity, it could take 24 hours or more before the sensor reads accurately. In some people, they never get a good result.
there is a great tech document here http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2903977/ explaining some of the kinetics.