Libre Sensor vs. Glucometer on Hypo Events

[Jasmin2000]

For 3 years my daily exercise has been to eat a banana and then burn the glucose on my exercise bike. I take Glucmeter readings to make sure timing of food and exercise intensity is right and I keep in range, especially in the half hour afterwards when BG is still falling, where I may do a BG every 5 mins.

Now have a Libre and it's telling me that in that half hour after exercise my reading is 3.2-3.8 yet my Glucometer never goes below 4.5-4.8. This is not a lag effect as the hypo readings would occur on the Glucometer first but they don't. My sensor says I've had one of these hypos every time I exercise but my BG has never shown this.

Is Libre known to give artificially low readings after a descending blood glucose trajectory or are the devices simply ot measuring the same thing - and which is right?

 

[Deleted member 527103]

There are limitations on CGMs which, unfortunately, many DSNs and CGM manufacturers do not share.
One of these is the way that CGMs, such as Libre, deal with the lag between changes in BG and changes in interstitial fluids by predicting the current value. This is great when BG is stable or changing slowly. When our BG changes direction or changes quickly, this prediction may not match as accurately.

Another limitation is “insertion trauma”. Some of us find that CGMs can be less accurate on the first day or two after insertion due to the trauma of having an alien object inserted in our arm.

 

[Jasmin2000]

Manufacturers are concerned with profit over patient care and once the device is approved their focus is selling it to the GP.

And apparently it works as my DSN is totally sold on the Libre and won't hear a word against it. When I told her about the lag and tried to explain that a CGM doesn't measure BG like a Glucometer she stopped our meeting. I'm rather dependent on forums like this to get the low down.

One of these is the way that CGMs, such as Libre, deal with the lag between changes in BG and changes in interstitial fluids by predicting the current value. This is great when BG is stable or changing slowly. When our BG changes direction or changes quickly, this prediction may not match as accurately.

Indeed - yet you can't set an alarm for the rapid change even though the LIbre has a ,downward arrow - but we have alarms to tell you that you're already in hypo - duh

 

[Deleted member 527103]

Indeed - yet you can't set an alarm for the rapid change even though the LIbre has a ,downward arrow - but we have alarms to tell you that you're already in hypo - duh

If you are happy with unofficial apps, it might be worth looking at something like xDrip+ (for an Android). It is some time since I used it but, as well as allowing calibration against finger pricks, I think it has different alarm options.