Libre patch v Blood glucose meter

[helli]

@Kev C did you take into consideration the known limitations of CGMs when doing the tests?
- did you give the Libre time to bed in?
- did you restrict the tests to “normal” numbers?
- did you ensure your blood sugar levels were stable rather than rising or falling?
- did you consider using an alternative app which supports calibration?
- did you take into consideration the acceptable error range (15%) of meters?

There are reams of pages explaining these limitations and how to get the most out of Libre and other CGMs by taking these known limitations into consideration rather than getting upset because your finger pricks says 12.1 and your Libre says 14.5 and falling fast within a couple of hours of applying it, for example.

If you understand the limitations, Libre can be very useful. So useful that your consultant is out of date: you do not have to finger prick to drive, the DVLA has caught up with 2020 technology.

 

[rebrascora]

I second what @helli has said. Libre has limitations but once you understand them, it is a great bit of kit .I can happily go days without needing to finger prick at all. I usually give the sensor at least 12 hours to bed in before I activate it and then I will wait until my levels are nice and stable and mid range.... say low 6s or high 5s with an horizontal arrow and very similar readings like that for at least half an hour and then I compare it to a finger prick. The Libre will usually be reading between 0.5 to 1mmol below my finger prick result but sometimes it can be between 1 and 2. I do a second "calibration check" a few hours later when my levels are stable and in range again, or the next day. The results will usually be quite similar in that if it read about 0.5mmols low the first time it will usually be about the same Maybe anywhere from 0.2 to 0.7 below.... it has to be done when my levels are nice and stable and in range. If they are changing significantly then all bets are off and I don't try to assess the calibration... Libre usually reads slightly lower than BG for me and most people find this. I am then confident to bolus from it and only occasionally double check hypos or hypers before treating although if you follow the guidance you should always be double checking hypos and hypers before treating. If it is consistently reading more than 2 mmols out I will report it to Abbott and get a replacement. Very rarely I get one that reads slightly higher rather than slightly lower and that can be a bit of a pain because I have learned to mentally adjust for it reading slightly low..... so if it says my levels are 3.8 they will usually be 4.5-4.8 and there is no major concern and I usually have secondary release carbs like a prune rather than really fast release like glucose or JBs, but when I get the odd one which reads high I have to remember that a 4.5 reading might actually be a hypo and may need JBs. I am however fortunate that I have pretty good hypos awareness and therefore I can respond to how I feel.

I wonder if you have not had enough training or education on the use of Libre and therefore your expectation was awry. The Libre Academy on Abbott's website is free to enroll and you can work your way through the modules at your own leisure. I also found reading other peoples' experiences here on the forum prepared me for not expecting totally compatible results and what was acceptable variation and when to check.

I would also say that if you had continued your experiment by testing different fingers of the same hand against each other as well as against the Libre, you might also lose confidence in your Glucometer as that can also produce a significant variation even in the space of a few seconds. Nothing is absolute. There are error margins in both sets of testing kit..... it is just that you have built up more trust in your glucometer over the years than the Libre. You also have to consider that blood is not homogenous, so the blood in your arm might be slightly different to blood in your left ring finger which interestingly might be quite different to the reading from your right ring finger and that slight variation will transfer into the interstitial fluid.
It is also important to know that the Libre reading you see has been processed through an algorithm to try to convert it to a BG reading rather than interstitial fluid which lags about 15 mns behind BG so it is extrapolating in order to predict what your level might be in 15 mins. If your levels are changing rapidly and not linearly then this prediction may be wrong. This is particularly so when the direction of travel of BG suddenly changes due to perhaps you taking a hypo treatment or insulin. In the hypo situation, Libre will continue to show/predict your levels dropping when the carbs are actually kicking in and bringing you up. This is the reason why you are advised to double check any low or high levels with a finger prick and also check your hypo recovery with another finger prick 15 mins later rather than rely on Libre as Libre will usually suggest that your levels are still dropping at 15 mins after treatment. Libre will eventually catch up with what is actually happening and get back on track but these occasions need finger pricks and you should have been made aware of that.

I really hope you can get over this distrust as the information Libre provides is amazing once you understand it's limitations and how to use it to best effect and enables us to become the experts in our own diabetes management and to do so much more effectively on a day by day and more importantly, night by night basis than has not been possible before.

 

[Kev C]

Thanks, both Helli and Barbara for the interesting and informative information you provided. I've been busy travelling, decorating, gardening, visiting relatives, playing sport etc. over the last few months, so apologies for not replying sooner, particularly the 6 questions you (Helli) asked me - Yes to all of them. I don't think it is such a huge problem if my finger prick for my glucometer showed 12.1 and Libre showed 14.5, but it is definitely a problem as far as I'm concerned once we go into single figures. I previously mentioned that I was advised to do a finger prick on my glucometer before driving and I'm glad I did as on one particular occasion, before driving my car, my Libre reading showed 5.0 and my finger prick for my glucometer at the same time showed 3.3! Very concerning from my point of view, so I immediately had a glucose 'fix' and waited until my blood glucose had risen and it was safe for me to drive. This was one of the reasons why I gave up my Libre patch, but I'm pleased that the Libre patches work for you both. 🙂