Hi Everyone, I’m just wondering if anyone can offer any advice to me about my new freestyle libre 2……my diabetes team were happy enough with my progress and grasp of all things T1 that they fast tracked me for the libre, which I picked up on Friday afternoon. I popped the sensor on (slightly painful), let it rest for a couple of hours and then activated it. All rather exciting! Dutifully set the low/high alarms and carried on with my day. All was well until the early hours of Saturday morning when the alarm started beeping and telling me I was low. Did a scan, 3.7, did a finger prick, 5.2. Didn’t get a chance to do a follow up scan to see if the libre had fallen in line with the finger prick reading as within 10 minutes the alarm started going off again. In fact, this happened 3 times within the space of about 2hrs, and then again when I was up and about a few hours later. All scans were 3.7/3.8, all finger pricks in the region of 5.4-5.9. A look at the libre link up app on my partners phone revealed that the libre was detecting levels of 2.9 at one point, which I would definitely know about as I’ve been that low before and it doesn’t feel good! Same thing happened this morning, alarm for low reading, scan was 3.7, finger prick was 5.6. Am I going wrong somewhere, have I maybe got a dud sensor or is this just a settling in period where there will be inaccurate readings for the first few days? Until I know I can place a substantial amount of trust in the libre readings I’m still pricking my finger to be on the safe side (especially before meals as I don’t want to risk an insulin induced hypo!) Thanks in advance and enjoy your Sunday. Nelly. X
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Libre inaccuracies?!
- Thread starter Nelly-Lou
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Welcome to Libreland @Nelly-Lou .
I found Libre is least accurate when
- first inserted. I find it takes 48 hours to settle so I tend to insert my sensors 2 days before activating them. For 2 days at a time, I have an active sensor in one arm and another in waiting on the other arm.
- when low or high. I always check the Libre with finger pricks before making a correction (either extra insulin to correct a high or glucose to correct a low)
- when pressure is applied to a sensor. This is so common that it has a name - “compression low”. When pressure is applied the sensor records a false low. This happens most at night if we lie on our arms whilst sleeping. Over time, I have got used to the best part of my arm to place my sensor to avoid this. For me it is as high as i dare without going into my shoulder and slightly under my arm. We all sleep differently so the best place varies.
- when the trend of our readings vary. CGMs and Libre do not directly read blood glucose. They read interstitial fluid which is about 15 minutes behind finger prick readings. Libre 2 attempts to take this delay into consideration by predicting the missing 15 minutes by extrapolating the current trend of readings. If that trend changes, e.g. when correcting a hypo, Libre will be inaccurate. Some people have seen this when they are spiking high - Libre will extrapolate and report a high reading that is never reached.
Libres are factory calibrated. This is supposed to be an advantage but it assumes we are all the same as Factory Man. I do not find this to be the case. In addition, a daily calibration gives me confidence in the sensor. For this reason, I use an unofficial app called xDrip which uses a different algorithm to convert interstitial fluid readings to blood glucose readings. This uses calibrated readings.
It takes a while to get used to Libre’s foibles. I hope you find it is worth it.
I found Libre is least accurate when
- first inserted. I find it takes 48 hours to settle so I tend to insert my sensors 2 days before activating them. For 2 days at a time, I have an active sensor in one arm and another in waiting on the other arm.
- when low or high. I always check the Libre with finger pricks before making a correction (either extra insulin to correct a high or glucose to correct a low)
- when pressure is applied to a sensor. This is so common that it has a name - “compression low”. When pressure is applied the sensor records a false low. This happens most at night if we lie on our arms whilst sleeping. Over time, I have got used to the best part of my arm to place my sensor to avoid this. For me it is as high as i dare without going into my shoulder and slightly under my arm. We all sleep differently so the best place varies.
- when the trend of our readings vary. CGMs and Libre do not directly read blood glucose. They read interstitial fluid which is about 15 minutes behind finger prick readings. Libre 2 attempts to take this delay into consideration by predicting the missing 15 minutes by extrapolating the current trend of readings. If that trend changes, e.g. when correcting a hypo, Libre will be inaccurate. Some people have seen this when they are spiking high - Libre will extrapolate and report a high reading that is never reached.
Libres are factory calibrated. This is supposed to be an advantage but it assumes we are all the same as Factory Man. I do not find this to be the case. In addition, a daily calibration gives me confidence in the sensor. For this reason, I use an unofficial app called xDrip which uses a different algorithm to convert interstitial fluid readings to blood glucose readings. This uses calibrated readings.
It takes a while to get used to Libre’s foibles. I hope you find it is worth it.
Thank you @helli for such a helpful response! I think the main culprit for me could be the “compression low” as I have been putting an old sock (clean, of course!) over it at night time as I was worried I might knock it during the night as I move around a lot in my sleep. Whilst not overly tight, it will have been compressing the sensor so could be what has been causing the problems. As I’m back to work tomorrow (I’m a nanny) I’m going to cover it with a breathable dressing so little hands are not tempted to poke at it. Luckily the youngest child that I look after is very switched on to my diabetes and takes a lot of interest in finger pricks and even counts to ten for me when I do my insulin which is really rather sweet. He’ll be very excited to see the special dot on my arm!!!! I’m sure over time I will become a lot more confident and not need it covered at all but at the moment I’m being a bit precious about it because it’s all so new. Just out of curiosity a short while ago I did a finger prick and then a scan and they were within 0.2mmol of each other so could mean things are finally starting to settle. X
Kaylz
Well-Known Member
- Relationship to Diabetes
- Type 1
@Nelly-Lou you can buy armbands to keep them safely in place, far better than using dressings etc, I use them24/7 (when I'm wearing a Libre but have become fed up with them so been without for over a week) xx
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Hope your sensor settles and begins to give you helpful information @Nelly-Lou
If the level of difference continues, do contact Abbott via their phone line who will troubleshoot the sensor and replace it if it isn’t performing within expected parameters.
If the level of difference continues, do contact Abbott via their phone line who will troubleshoot the sensor and replace it if it isn’t performing within expected parameters.
Thank you @Kaylz and @everydayupsanddowns, I’ve just been on the phone to Abbott and they are sending a replacement. I’ve also emailed my DSN to ask for a call about it just to ease my mind a bit. Had another hypo alert this morning but a finger prick revealed me to be 6.3. I’d love to give the dexcom a go as have heard nothing but amazing things about it but sadly it’s not available on prescription in my area unless you have zero hypo awareness and I can’t afford to self fund at the moment 
x
x
nonethewiser
Well-Known Member
- Relationship to Diabetes
- Type 1
0.2 is about as good as it gets. Know from past experience using tight dressing on sensor results in low readings, so go for larger one next time.
Since changing to libre 2 find accuracy great, much improved from 1 version. Like alarms functions, something that should have been on device from start.
@nonethewiser things seem to be settling now, I had an exact match to a finger prick last night and this morning there was 0.1mmol difference. Haven’t put a band/cover on the libre since the weekend and am barely even noticing it now. Feel bad that Abbott are sending a replacement now that things are falling into place but I suppose it’ll be good to have a spare as my local doctors surgery and pharmacy can be a bit slow on getting prescriptions sorted…..I had to chase them a fortnight ago for my novopen echo and insulin cartridges that the hospital had sent them a letter about at the start of the month. X
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