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

Since switching to libre 2 plus, I haven't had a single CGM that has been close to my finger prick tests. My CGMs are consistently showing readings between 1 and 2 mmol lower. It's really annoying when the CGM gives you a false sense of glucose control
 
Yup, agreed @mariavontrapp
Things that seem to make it wonkier: sunshine, walking more than 2 minutes, being horizontal, * looking * at a packet of biscuits....

I read this recently and it was a good reminder not to rely solely on CGMs

Diabetic ketoacidosis due to a sensor defect of FreeStyle Libre: A case report - PMC

The FreeStyle Libre Flash Glucose Monitoring System allows users to obtain sensor glucose values by scanning with the reader or their mobile phone. We report a case of a 59‐year‐old man with type 1 diabetes mellitus who developed diabetic ...
pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov
 
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^ having said that, I've realised that using hand sanitizer to clean my finger for a "proper" test when out and about isn't really working as well as I'd thought - thought to double check at home this afternoon when my libre showed 3.7, and got a 5.3 with hand sanitizer (ha! Libre discrepancy!), then properly washed my hands and got a 3.6.
Face, meet palm...
 
Libre 2+ was reading 3 units lower than a properly-washed-hands fingerprick this morning; 4 units lower an hour ago, 4.5 units lower just now (on day 8 of wearing). Ridiculous.
 
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Mine has given me spurious low readings for the last few sensors, usually around 3-4am. It's often 2+mmol/l lower than a finger prick. Yesterday I got 3.4 from the CGM and the finger prick was 9.1! Looking back at the graph later, that shows a reading of around 6 despite the log in the app showing the low number. I've had it where low readings are there for about 30 minutes and then when you review things later they aren't shown at all and what the graph shows is much more like what actually happened vs the instantaneous readings. Abbot have replaced sensors without question but it is a bit annoying. They have asked for this one to be sent back to them for analysis which is a positive. It's so frustrating to be woken up a couple of times in the night for false alarms. I'm fairly new (4 months) to T1D and this is making it harder adapting.
 
ErinRodas said:
Just wanted to chime in, your CGM reads glucose from interstitial fluid (basically the fluid between your cells), which tends to reflect your glucose levels a bit differently than finger sticks. That’s why CGM readings and finger prick numbers don’t always match, blood glucose can lag behind by a few minutes. If you're getting weird or fluctuating readings that don't match how you're actually feeling, it might be that your sensor shifted or got a bit loose. That’s happened to me a few times, and it really messed with the accuracy. I started using Not Just a Patch its an over-patch that covers my sensor keeping it secure, and it made a big difference. I’ve been using them for about a year now, they’re super reliable and totally worth it. You can order online, and they’ve got options for different CGMs. Definitely worth checking out if you’re running into this issue!
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Honestly, the thought of my sensors coming loose has crossed my mind when the reading variations have skewed over 2mmol. I do frequently get them caught or knocked on stuff and that has pulled the adhesive off the sensors in some places. But because the sensors have still felt secure when I've checked them and the sensors' behaviour hasn't immediately changed, I've never been 100% sure. Doesn't help that it's happened even when I think my sensors haven't been knocked or caught on anything.

Still, I've considered getting something to hold my sensors in place for a while anyways, so thank you for the recommendation. I've ordered a sample patch to use for my next sensor, so I'll see if it does make a difference to my readings. But if it doesn't, at least I'll have something to keep my sensors secure and protected.
 
Dave Metric said:
Mine has given me spurious low readings for the last few sensors, usually around 3-4am. It's often 2+mmol/l lower than a finger prick. Yesterday I got 3.4 from the CGM and the finger prick was 9.1! Looking back at the graph later, that shows a reading of around 6 despite the log in the app showing the low number.
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This sounds like the false readings could be being caused by a compression low. Sometimes when people sleep on the arm their sensor is on, the pressure applied to the sensor can cause false drops in readings. Also, because the sensors track the glucose levels through the interstitial fluid in the body rather than the blood like the finger prick tests do, there are times where large variations in readings can occur when levels are moving rapidly. It's claimed there's around a 10 to 15 minute lag between the sensor and the finger prick and that the sensor is usually behind the finger prick, so this is usually why the graphs don't always record readings that you've scanned (I have this happen all the time; it can be a pain). If this happens again, it might be worth waiting 10 to 15 minutes after doing a finger prick just to see if your sensor reading catches up.
 
It's been a while, so I figured I'd update this thread with a recent development I've had regarding my sensors.

Over the past month, I've used sensor patches to see if having something holding my sensors in place would improve my readings' accuracy. I'm not sure if the person who originally suggested this to me was being genuine or turned out to be a spammer, but I had been considering looking for sensor patches prior to then anyways. I cannot tell you the amount of times I catch these darn things on clothes or doorframes, etc and then have found myself questioning if my sensor was okay or not. I figured I had nothing to lose by trying to rule this out.

Good news: the reading variations have improved for my last two sensors. Sensor number one lasted the full fifteen days and stayed under 1mmol difference between my sensor and finger pricks. And sensor number two, the one I'm currently wearing, is on Day 13 and still doing great. Compared to the first sensor, its behaviour has been a little more erratic. But the variations between the sensor and finger prick tests have stayed quite close (under 1mmol most of the time too) and haven't strayed too far for too long, so I see that as an improvement.

Of course, it's still too early for me to concretely say for sure that loose sensors were the problem for me. It could be a fluke. But things are going good so far, all things considered. I'm continuing to monitor the situation all the same. Fingers crossed my good luck continues into the next month too.
 
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