Hi there, I’m new to using the Dex G5 and Tandem X2 Slim pump combo. Whenever I enter a calibration number into the pump and the smart phone/iPhone, the Dexcom app and Tandem pump will average between the number from my meter and the current number on the Dexcom. So for instance if the meter says 100 and the Dex says 85, when I enter calibration number from the meter the pump and iPhone app will change to 92, not 100. If I enter the number again/a second time, they will go ahead and match the number of the meter. I’m wondering if any of you noticed the same issue, and what is the recommended way to deal with it? Let it run with the averaged number between the current Dex and the meter, or should I always input the meter value a second time and force it to match the meter? Thank you for your help!
This is actually somewhat expected behaviour - it would take multiple successive calibrations, usually a few minutes apart from one another to try to get it to be close to the exact reading you’d get from a blood glucose meter.
A few things to remember here though:
- The Dexcom (or any CGM for that matter) reads your blood glucose from interstitial fluid, not blood, so it will be slightly delayed in terms of instantaneous blood glucose value anyways. It’s very useful for trending information - like is your blood glucose dropping, or climbing, and how fast? But won’t give you lab accuracy to where your blood glucose currently sits - nor does your glucometer.
- Your blood glucose meter’s accuracy isn’t as precise as you’d think it is - it’s usually “accurate to within 10%.” Sometimes more, sometimes less. Any number of factors can affect this - many of which aren’t even within our control. The CGM is similar in that it’s accurate within a tolerance.
- A CGM sensor generally becomes more accurate over time. It’ll be least accurate at the beginning and end of it’s life, and most accurate in the middle.
I’d actually recommend against “over calibrating” your device, especially when it’s just been inserted or is near the end of it’s life. This can cause some pretty wild results. I personally find it best to only calibrate when it asks for it, of if I get a wildly wrong reading.
Also leave a bit of time in between calibrations, except the two startup ones required to initialize the sensor. 10-15 minutes allows the sensor to gather it’s own readings in between calibrations and then it averages itself out.