I am definitely aware of the Conventional Wisdom around CGMs... calibrate when BG is steady (but I'm in the middle of a meal and my pump keeps telling me to METER BG NOW!!) ... use it for trends ... don't make clinical decisions based on it... and so on and so forth. I know that if I do two fingersticks within seconds of each other, the results will vary slightly, and the variation on the CGM applies more -- though the CGM variation is more time-sensitive (meaning it's giving a ballpark reading a moment in time... it's not giving a "within 20% reading" or a steady measurement of 120 would appear to be bouncing between 108 and 132 constantly.
But sometimes I appear to be running a steady 120 and then my meter tells me I'm at 150. And that ain't right -- the discrepancy isn't due to a time lag.
Acid, I wonder what you mean by "fiddle with it to make them match"....are you telling me you only calibrate a CGM displaying 80 with a meter reading of 80? I'm not sure what good that does (though I really respect your opinions from everything you've shared on Tu!). I must be misunderstanding.
Rich, I always use fingers to test BG. I've never done any of that "alternate site testing" (forearm) that seems to be all the rage these days. That actually seems more painful to me!
Niko, I agree with you on all points. But sometimes when I am being ordered to recalibrate (now I try to "beat the timer" but it doesn't always happen) it's not a good time to do so, so I try to make up for it with another calibration soon after. It doesn't always work. If the CGM is wildly off, sometimes I'll trick it and "Start New Sensor" with a fresh calibration, forcing all previous ones to be discarded.
Nel, 15 minutes PRIOR TO a meal? That might be the best time, but it isn't particularly economical, considering I'll also test AT mealtime in order to bolus. I don't like using a fifteen-minute-old reading for the purpose of a possibly large bolus.