How big a difference between DEX and BG Meter

I'm new to CGM'ing now on my 2nd sensor. How a big a gap between sensor reading and BG meter reading do you find acceptable? When do you start worrying and what do you do? Recalibrate?

So far I've seen reasonable differences, (following all in mg/dl), sometimes within 5 points, others 10 to 20. But at times it has been much larger. It seems when my BG is above 200 the difference grows. So I would like to know what others do.

Thanks for any tips.

Generally my fingersticks and dexcom are close enough that I don’t worry about it, but I find that the biggest differences tend to occur when my blood sugar is rapidly changing, and then I leave it alone and they’ll usually come together eventually. If I wake up first thing in the morning and there is a huge gap, sometimes I’ll test two or three times to get an average (and make sure it’s not a one-off) and then I’ll recalibrate, even if it’s only been a few hours since my last calibration. And yes, I’ve seen bigger gaps the higher my blood sugar. I think Dex is supposed to be more accurate on the low end. And sometimes, especially if it’s been more than two weeks, it’s just time for a new sensor :). Good luck!

Most glucose readers are known for worse readings as you go higher. So it's acceptable for a larger difference as you calibrate while high. Just wait and recalibrate when you are lower to get a better calibration.

how much diff between CGM and meter readings -- if it's way off, I agree withe Shelby76 -- recheck BG 2 more times to see an average. And first thing in the morning, my CGM typically but not always is lots lower than the BG -- eg, CGM might be 76 and BG 109.

I calibrate Dex if it is more than 20% off from my fingerstick reading. It is rarely that far off but that is the recommendation of Dexcom so I follow it. I try to calibrate during periods of no change so when I first wake up in the morning or 3-4 hours after a meal or bolus. I never calibrate when there is an up or down arrow because my blood sugar is changing too much and Dex will just get confused.

You just gotta test during rapid increase and decrease. It just won't follow those large, fast changes quickly enough.

I’m with Clare, as long as the difference is less than 20% I don’t worry about it. The trend is what to watch for. As BG comes down the differences get smaller.