CGM v finger stick reading differences

[Fuggs]

I've noticed quite a large reading variance on my Libre 2 cgm and my regular stick.
For example this morning my blood with the stick was 5mmol and 7.9 with the cgm.
Has anyone else had this issue?
Thanks

 

[Rachox]

There is an allowable variance between all types of blood glucose reading methods. As a type 2 on a small dose of medication and a low carb diet, I just stick to one measuring device to look for immediate reactions to meals and general trends in my glucose management, rather than absolute values. Interestingly I have just switched from the Libre 2 plus to the Dexcom One +. The Dexcom allows you to calibrate the sensor to match your finger prick test.

 

[Melgar]

As @Rachox says there is an allowable difference of 15% +/- on any device. There variables to take into account for measuring devices. The master devices which are the most accurate, are kept in climate and temperature controlled conditions. So there will always be some measure of inaccuracy for common usage devices, hence the allowable 15% +/- readings.

Another point is your cgm doesn’t test blood, it tests interstitial fluid . Therefore there is a time lag of up to 15 mins in the readings between your cgm and a blood reading from your finger prick device. Your finger prick device gives you an instant reading because it’s testing blood.