Libre 2 Plus - Worsening variation between sensor readings and glucose meter readings after around 8 days

[Introverted_And_Proud]

So, I have vaguely posted about this issue before in other threads about the Libre, but I wanted to post about it here in more detail just to get a little insight from users going through a similar problem.

For context, I’m a former user of the Libre 2 sensors, recently switched to the Libre 2 Plus sensors by my GP in light of the discontinuation of the former. I’m also a user of the Accu Chek Aviva Expert meter, which I’ve had for six years now. Since the end of 2024, I noticed that the difference between my Libre 2 sensor readings and my meter readings tends to get worse. In the first seven days or so, the difference stays consistently within 2mmol for each of my meals and before bed, with the occasional odd difference here and there depending on my blood sugars’ behaviour. But usually, the line of the graph follows closely with the rises and the falls. However, within the latter days of its life, the sensor readings (presumably due to frequent usage) start to stray away from the meter readings, going up to 3 to 4mmol lower than my meter and failing to catch up properly after 15 minutes. I thought that upon switching to the Libre 2 Plus this might resolve the problem, but the same thing has been happening. There have been times where the sensors have started doing this earlier or later than 8 days, sometimes as early as two or as late as four, but most of the time it’s around halfway. Within this year alone, only one sensor made it the full lifespan without any issues. The rest I‘ve ended up changing after about a week.

The frustrating thing is, the sensors aren’t faulty in the sense that they stop working entirely or I have constant connection issues with Bluetooth. In the beginning, they work great. They just cause false readings, rises and drops after a certain amount of time has passed. Which is aggravating for me, as I’m Type 1 and use the Libre to monitor the behaviour of my food and insulin, so it is making my treatment decisions very difficult when I can’t actually tell how high or low my levels are going on certain days. I wouldn’t mind the variations so much if the sensor did correct itself or it was only the odd false reading at certain times, like, after eating or something. But it’s very disrupting having to constantly finger prick because my sensor is reporting false hypos or incorrectly claiming my levels aren’t rising or falling when they actually are, outside of messing up my data on the app as a whole.

Has anyone else experienced this problem and has any tips on how to improve it? I’ve tried putting my sensors on a couple of days earlier to see if that helps, but it’s only good in setting my readings straight within the first 48 hours. I’ve also stopped scanning unless it’s to correct signal loss, which doesn’t seem to help either. And as far as my meter goes, I do frequent control solution tests, so the meter itself and the test strips I use are good.

Is it possible it’s not a sensor issue and I’m just not reacting well to the sensors as a whole? I know some people‘s experiences with CGMs can vary, but they seem to work fine at first.

Could it be the placement of the sensors? I do move them to different spots on my upper arms but it doesn’t seem to matter.

Maybe it’s the time I activate the sensors? I usually try to do it between 4pm and 4:30pm, around an hour and a half to two hours after my lunch.

Any advice or suggestions are appreciated.

 

[grantg]

some like to insert the sensor a day earlier alongside having a flat graph at the time of activation. worth trying that however for me experience is its been off by a fair bit (even taking into consideration time lag), reading alittle lower.. for some others it can read higher. theres alternative apps (which abbot wont recremmend) which you could calibrate ... however imo not worth that if calibrate and its wrong it could lead to even more variability between fingerprick + cgm

 

[Jaylee]

So, I have vaguely posted about this issue before in other threads about the Libre, but I wanted to post about it here in more detail just to get a little insight from users going through a similar problem.

For context, I’m a former user of the Libre 2 sensors, recently switched to the Libre 2 Plus sensors by my GP in light of the discontinuation of the former. I’m also a user of the Accu Chek Aviva Expert meter, which I’ve had for six years now. Since the end of 2024, I noticed that the difference between my Libre 2 sensor readings and my meter readings tends to get worse. In the first seven days or so, the difference stays consistently within 2mmol for each of my meals and before bed, with the occasional odd difference here and there depending on my blood sugars’ behaviour. But usually, the line of the graph follows closely with the rises and the falls. However, within the latter days of its life, the sensor readings (presumably due to frequent usage) start to stray away from the meter readings, going up to 3 to 4mmol lower than my meter and failing to catch up properly after 15 minutes. I thought that upon switching to the Libre 2 Plus this might resolve the problem, but the same thing has been happening. There have been times where the sensors have started doing this earlier or later than 8 days, sometimes as early as two or as late as four, but most of the time it’s around halfway. Within this year alone, only one sensor made it the full lifespan without any issues. The rest I‘ve ended up changing after about a week.

The frustrating thing is, the sensors aren’t faulty in the sense that they stop working entirely or I have constant connection issues with Bluetooth. In the beginning, they work great. They just cause false readings, rises and drops after a certain amount of time has passed. Which is aggravating for me, as I’m Type 1 and use the Libre to monitor the behaviour of my food and insulin, so it is making my treatment decisions very difficult when I can’t actually tell how high or low my levels are going on certain days. I wouldn’t mind the variations so much if the sensor did correct itself or it was only the odd false reading at certain times, like, after eating or something. But it’s very disrupting having to constantly finger prick because my sensor is reporting false hypos or incorrectly claiming my levels aren’t rising or falling when they actually are, outside of messing up my data on the app as a whole.

Has anyone else who has experienced this problem and has any tips on how to improve it? I’ve tried putting my sensors on a couple of days earlier to see if that helps, but it’s only good in setting my readings straight within the first 48 hours. I’ve also stopped scanning unless it’s to correct signal loss, which doesn’t seem to help either. And as far as my meter goes, I do frequent control solution tests, so the meter itself and the test strips I use are good.

Is it possible it’s not a sensor issue and I’m just not reacting well to the sensors as a whole? I know some people‘s experiences with CGMs can vary, but they seem to work fine at first.

Could it be the placement of the sensors? I do move them to different spots on my upper arms but it doesn’t seem to matter.

Maybe it’s the time I activate the sensors? I usually try to do it between 4pm and 4:30pm, around an hour and a half to two hours after my lunch.

Any advice or suggestions are appreciated.

Hi,

Sorry you’re having discrepancy issues with the libre.

From my understanding, the sensor will read & send its interpretation of the data regardless of which app is picking it up.
Some 3rd party apps can be calibrated. (I know of 2 that can “xDrip” & “Diabox.”)

I feel uncomfortable asking this question.
Could you have lost body fat tissue from where you normally place your sensor & it’s probing a little muscle tissue??

 

[Introverted_And_Proud]

Hi,

Sorry you’re having discrepancy issues with the libre.

From my understanding, the sensor will read & send its interpretation of the data regardless of which app is picking it up.
Some 3rd party apps can be calibrated. (I know of 2 that can “xDrip” & “Diabox.”)

I feel uncomfortable asking this question.
Could you have lost body fat tissue from where you normally place your sensor & it’s probing a little muscle tissue??

Hi there. Thanks for the response.

I will admit I've always been underweight for my age (worsened by my diabetes because of how much I've had to cut out of my diet to keep my levels under control), so I do lack body fat in most places, my arms included. It is not uncommon for me to hit muscles during insulin injections or when applying my sensors. I can usually tell when I do because it hurts or bleeds a bit afterwards, in which case my sensor variations from my finger prick tend to get worse much earlier on in its lifespan. Otherwise, if my sensor application was painless and bloodless, my sensors tend to be okay until around 8 days in, sometimes a bit longer.

 

[Introverted_And_Proud]

some like to insert the sensor a day earlier alongside having a flat graph at the time of activation. worth trying that however for me experience is its been off by a fair bit (even taking into consideration time lag), reading alittle lower.. for some others it can read higher. theres alternative apps (which abbot wont recremmend) which you could calibrate ... however imo not worth that if calibrate and its wrong it could lead to even more variability between fingerprick + cgm

Hi there. Thanks for the response.

It's, unfortunately, impossible for me to put my sensor on at a time where my readings could be flat because they usually aren't. They spike and drop a lot despite my attempts to mitigate it, and while the false readings can't follow the pattern properly, the line on the graph still shoots up and down in turn. My readings are never flat and likely never will be. Lol. XD

Regarding the calibration apps, I agree that it probably isn't worth me trying. As previously stated, my sensors tend to be fine within the first week of use and only start to taper off near the end of its lifespan, so I fear meddling with the app using a third party app could actually worsen it. Plus, as you say, they're not approved by Abbott and I'm not tech savvy. It's best I don't risk messing with anything I don't understand nor could cause issues with the app.

Thank you for the suggestions, in any case.

 

[Jaylee]

Hi there. Thanks for the response.

I will admit I've always been underweight for my age (worsened by my diabetes because of how much I've had to cut out of my diet to keep my levels under control), so I do lack body fat in most places, my arms included. It is not uncommon for me to hit muscles during insulin injections or when applying my sensors. I can usually tell when I do because it hurts or bleeds a bit afterwards, in which case my sensor variations from my finger prick tend to get worse much earlier on in its lifespan. Otherwise, if my sensor application was painless and bloodless, my sensors tend to be okay until around 8 days in, sometimes a bit longer.

Ok.
We seem about the same body composition… (I’m a bloke.)
Are you hydrated enough?
Exploring any factors.

A 3rd party app does not interfere with the running of the official Libre link app.
It runs alongside?
Infact I don’t tend to open the Libre app unless I start a new sensor or need to reconnect.
I rarely need to open the other app either as it allows me a readout on my home or Lock Screen or a reading sent to another device like a wearable..

 

[Introverted_And_Proud]

Ok.
We seem about the same body composition… (I’m a bloke.)
Are you hydrated enough?
Exploring any factors.

On average, I consume around four cups/mugs of liquid a day; two cups of tea (with milk) and two glasses of cordial (water + fruit juice), which I admit is less than what I should be consuming. Though, I do eat some foods that give me a little extra liquid intake, like fruit and veg, or milk with my cereal, for example. The only time I do tend to drink a bit more is during warmer weather. However, I don't usually suffer with symptoms of dehydration, so I think I'm fine? The only real time I have dehydration-like symptoms is when my blood sugar levels are high, which has nothing to do with my liquid intake as far as I can tell.

 

[Jaylee]

On average, I consume around four cups/mugs of liquid a day; two cups of tea (with milk) and two glasses of cordial (water + fruit juice), which I admit is less than what I should be consuming. Though, I do eat some foods that give me a little extra liquid intake, like fruit and veg, or milk with my cereal, for example. The only time I do tend to drink a bit more is during warmer weather. However, I don't usually suffer with symptoms of dehydration, so I think I'm fine? The only real time I have dehydration-like symptoms is when my blood sugar levels are high, which has nothing to do with my liquid intake as far as I can tell.

To be fair with high sugar levels, the body will be trying to expel it out.
Thus creating more urine. Which could contribute to dehydration if not topped up?
At least till BG levels come back into range..

That’s not to mention what’s lost through sweat in hotter weather as the body regulates temperature..

 

[Introverted_And_Proud]

To be fair with high sugar levels, the body will be trying to expel it out.
Thus creating more urine. Which could contribute to dehydration if not topped up?
At least till BG levels come back into range..

That’s not to mention what’s lost through sweat in hotter weather as the body regulates temperature..

To be honest, high blood sugar levels (10mmol - 13mmol, I mean) very rarely mess with my bladder. The most I get is a persistent dry mouth and throat that takes ages to go away, even after my levels are back to normal. I do carry bottles of water around with me regardless and do drink gulps of it in between my meals, either when I feel thirsty or feel I need to replace lost liquid. That amount equates to around 0.25L a day (I have 0.5L bottles and I'm ashamed to say I don't drink the whole thing in one day).

Still, I initially noticed the issues with my sensors occurring around Autumn time and they have continued to play out similarly even as the weather has gotten warmer, so I don't think hydration is the issue. Even when I have tried to drink more, I haven't noticed anything different with the sensors' behaviours.

 

[jabalka]

Hi, good people!


I recently started using the Libre 2 Plus sensors, having previously used the Libre 2, and I’ve noticed a significant difference in the readings compared to my glucometer. Here’s what I’ve observed:


Low Blood Sugar Readings
If my blood sugar falls within the normal range I’ve set (4.8mmol/L – 7.8mmol/L), the sensor’s readings are almost identical to those from my glucometer. However, when my blood sugar drops below 4.6mmol/L, the sensor starts to show values approximately 1mmol/L lower than my actual blood sugar level. The lower my blood sugar goes, the more decalibrated the sensor becomes.

For example, if my glucometer reads 4.5mmol/L, the sensor might display 3.2mmol/L. Even more concerning is when the sensor shows 1.8mmol/L (which seems to be the lowest value I’ve seen). Naturally, I panic and check with my glucometer, only to find that my actual blood sugar is slightly above 3.2mmol/L.

These discrepancies are unsettling, especially since my Diabetes Health Team assured me that the Libre sensor is 99% accurate and even suggested I rely solely on it instead of my glucometer. Of course, I won’t do that—even if it were truly 99% accurate, that 1% uncertainty would always haunt me. Yes, I’m a control freak, but in my condition, I have to be.


High Blood Sugar Readings
When my blood sugar is high, the sensor tends to be more accurate, rarely differing from my glucometer. However, once my blood sugar exceeds 15mmol/L, the sensor occasionally decalibrates by about 0.5mmol/L—though not consistently.

The most noticeable discrepancies occur when my blood sugar rises rapidly. In such cases, the sensor might overestimate my blood sugar level by 4-5mmol/L. For instance, if my actual blood sugar is 12mmol/L, the sensor might display a reading above 16mmol/L, with a tendency to keep increasing.

This only happens when my blood sugar spikes suddenly!




Now that I understand how the sensor behaves, I can work around its limitations. However, I still don’t fully trust it, despite my Diabetes Health Team’s recommendation.

For now, I will always double-check with my glucometer if a reading seems extreme!