Has anyone noted a difference between the Libre 2 sensor readings and finger Blood test

[T.D. & L.D.]

We have recently joined this group. My Wife has been a type 1 diabetic for the last 53 years. She has been using the Libre 2 sensor for the last three years.
We have noticed for some time that there can be some marked differences between the sensor and finger blood test readings.
1. Sorry if there has been some discussion on this before and we have missed it.
2. Has anyone else noticed this? If yes what sort of differential are you noticing? We have noticed on occasions 2 or 3 units, or more differences.

We should point out this is not all the time, but around food times ( if it should occur can cause the patient to inject the wrong dose of insulin.)
We have found that the sensor inaccuracy is not constant and therefore can cause mistrust of the system by the user.
We are trying to get our diabetic nurses and Abbott Labs to understand the problems that can arise from these issues.

Should you have come across this issue before, or are noticing it now, could you let us know here. We need more evidence that this a problem so we can do something about it.

 

[KennyA]

It's a known issue. CGMs like the Libre measure glucose in interstitial fluid: fingerprick measure blood glucose. Both systems have "acceptable" inaccuracies - the fingerprick, for example, has to be within 15% of the true value 95% of the time.

There are a number of threads on the forum about the issue - here's a link to one.

Home blood prick tests - a waste of time?

A year ago I was diagnosed with prediabetes. I worked at losing weight, bought one of those small testing kits and it showed that I was out of the prediabetes zone. I tested myself every week or two for a year, sometimes after food, sometimes first thing in the morning, sometimes any time of...

www.diabetes.co.uk

 

[Melgar]

Hi there @T.D. & L.D. as @KennyA says there is an acceptable allowance in error which is based upon a lab controlled meter.

One of the things I have noticed about the CGM devices is when your blood sugars are changing rapidly, around meal times or early morning readings, due to dawn phenomenon, the CGM tends to be less accurate. I think in part it’s due to the way the CGM collects and analyses your blood. Your finger prick readings from your glucometer are directly read an analyzed from your blood. The CGM , however, analyses the blood secreted into your interstitial space between your cells. There is a time lag due to the speed at which blood enters this interstitial space hence the difference in readings.

CGM devices have a reasonable accuracy rate around the normal blood sugars, but they become less accurate when your blood sugars drop or are high.

As always, the glucometer is the one to read, for such events like low blood sugars.