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Type 1 Freestyle Libre

Discussion in 'Ask A Question' started by MNO, Jul 19, 2018.

  1. MNO

    MNO Type 1 · Newbie

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    I have recently started using the freestyle libre glucose monitor instead of the blood testing kit AgaMatrix. I have had several occasions where I have questioned the result of the libre monitor and so compared the result to a blood test. I have not calibrated my testing kit for months but there is a large difference in result e.g. libre stated 2.9 and blood test kit was 8.8. I didn't feel low at the time but wasn't sure what my glucose was or whether to have sugar or not. Please advise on which I should be using or both, and why the results are so different.

    Thanks
     
  2. urbanracer

    urbanracer Type 1 · Moderator
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  3. EllieM

    EllieM Type 1 · Well-Known Member

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    Yes, freestyle libre doesn't work for everyone. If in doubt, believe the meter. To summarise
    1) freestyle is meant to match the blood sugar reading 15 minutes before the libre reading.
    2) many people find the first 24 hours are very inaccurate.
    3) some people find the last couple of days very inaccurate
    4) some sensors are dud.
    5) if you record the sensor readings against blood sugar readings for a couple of days (remember the 15 minute delay) and get serious discrepancies, you can phone Abbott and they'll probably replace the sensor for free.
    6) a few people (eg me after 8 months of good results) find they don't get decent results whatever they do, but I'd get a replacement sensor from Abbott before you assume that, as for most/many people it works very well.

    Good luck.
     
  4. noyahO21

    noyahO21 Type 1 · Member

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    I'm very disappointed with the Freestyle Libre sensors and have stopped using them. I've had Type 1 diabetes for 52 years since age 3. Having the Libre sensor was such a relief and so convenient after checking bsl for so many years. I found it particularly helpful during the night. I used the Freestyle Libre for almost a year before I discovered that it was completely inaccurate. My HbA1c gradually rose from 6.7 to 6.9 and then 7.5% before I realised something wasn't right as the Libre results didn't match the rise in my HbA1c. My Endocrinologist advised me to do one month of paired testing, i.e. used both the Libre sensor and did bsl checking together. The results clearing showed that the Libre sensor consistently read anywhere between 2 to 5 mmol lower than my bsl result - hence the reason my HbA1c rose.
    My daughter, 20, who was diagnosed with Type 1 diabetes just over a year ago, has also stopped using the Libre sensors after experiencing the same. I'm hoping one day it'll be more accurate.
    I'd be happy to hear from anyone who's experienced such discrepancies using the Libre sensors.
     
  5. helensaramay

    helensaramay Type 1 · Expert

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    @noyahO21 although this thread is nearly a year old, I think your comment deserves a response.

    Did you ever try any of the third party apps that allowed calibration against finger pricks like Glimp?
    I find this more accurate for me.

    Libre have recently updated their algorithm to make it more accurate. Have you used the Libre since the update to the app and reader?

    And I understand Libre 2 will be individually factory tested which should further improve the accuracy.

    In other words, the day when it is more accurate could well be now.

    Regardless of any of this, I always fingerprick test at least twice a day to check my sensor is not drifting out.
    As I use the Glimp app, this also acts as a calibration.
     
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  6. novorapidboi26

    novorapidboi26 Type 1 · Well-Known Member

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    @helensaramay does the glimp app work without a third party device.....or are you using it purely as a recording tool....and if so, how do you calibrate...?
     
  7. helensaramay

    helensaramay Type 1 · Expert

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    I use Glimp without MiaoMiao or anything - I just scan with my phone like you do with LibreLink.
    Glimp allows you to add finger prick readings (and other stuff which I ignore). It plots these on the graphs and, once you have input 3 readings (I think) it uses these for calibration.

    To do this, press the "+" at the top of the screen, enter the "Glucose" reading and then click the "floppy disk" save symbol atthe top of the screen.

    I tend to calibrate at the start and end of the day as this is when my BG is most stable.
     
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  8. Muneeb

    Muneeb Type 1 · Well-Known Member

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    I second helensaramay. Glimp is far superior for me, can use as normal with NFC or with miaomiao as a CGM. Can calibrate with meter and get much better accuracy. Can also use the app with data on any number of devices, I also have it on my smartwatch.
     
  9. Muneeb

    Muneeb Type 1 · Well-Known Member

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    I found this and you have to be careful, as I was too reliant upon it initially which almost led me to hypo unawareness. As helensaramay stated, I use GLIMP app and its much better.
     
  10. Muneeb

    Muneeb Type 1 · Well-Known Member

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    Just one thing to add, GLIMP is only for android devices, spike is for apple. Xdrip is a Glimp alternative for android which some people prefer.
     
  11. novorapidboi26

    novorapidboi26 Type 1 · Well-Known Member

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    So how do you calibrate with Glimp....?

    Define calibrate..
     
  12. Muneeb

    Muneeb Type 1 · Well-Known Member

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    Well its basically a fudge factor applied to a pre-set correlation that adjusts that correlation to fit what the meter is reading.

    In glimp you take a reading from meter and add it into the glucose reading section...
     
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  13. novorapidboi26

    novorapidboi26 Type 1 · Well-Known Member

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    Is that not just adding in a blood test reading.....does the app use that alongside the sensor reading......

    I confess I haven't played about with it.....I will tonight though...
     
  14. helensaramay

    helensaramay Type 1 · Expert

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    @novorapidboi26 Libre sensors are "factory calibrated".
    Finger prick meters are also done similarly but you can stick a testing strip in a calibrated solution to check the meter is reading correctly.
    Libre sensors are harder to do this with so you have to rely on the interstitial fluid reading it takes and how it uses this to calculate what your BG is.
    I believe the Libre takes a number of readings such as temperature and plugs these into an algorithm to give you the BG reading.

    Some of us seem not to match the factory calibrated person; we find the readings given by LibreLink and the Libre reader are constantly wrong ... and not by the same amount all the time.
    Some third party apps such as Glimp and Spike use slightly different algorithms to convert interstitial fluid readings in to BG readings. Part of this algorithm uses historic differences between finger prick readings and Libre calculated values to tweak the algorithm and, for me, provides a more accurate reading.

    Due to things like the delay between Libre readings and finger prick mean that the algorithm tries to take an average of a number of finger prick reading differences to come up with the closest approximation. I believe Glimp uses the last 3 finger prick readings. This allows for differences between sensors and for the sensors to slightly drift during their life,

    I try to enter my finger prick calibration readings at a time when I least expect my BG to be changing. So when I have not been eating, no insulin on board and not been exercising. As I spend most of my time grazing at my desk or exercising, the best time to do the calibration is first thing in the morning, before I have had breakfast.
     
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  15. Muneeb

    Muneeb Type 1 · Well-Known Member

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    You add the monitor reading, if its too far from the sensor reading in the app it will calibrate automatically. You don't have to do anything apart from put the readings in.
     
  16. Scott-C

    Scott-C Type 1 · Well-Known Member

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    The sensor generates a raw number based on how much glucose there is and then turns it into what it thinks is a bg number. But it can get it wrong.

    So, if you wait until your levels are fairly stable, there's a fair chance that bg and ifg will be about the same, so if, say, the sensor is reading it as 3.6 but a bg test shows it's 4.7, you type in the bg reading as a calibration to tell it, nah, it's not 3.6, it's 4.7, so the sensor will be more accurate in how it interprets the raw numbers it gets.
     
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  17. novorapidboi26

    novorapidboi26 Type 1 · Well-Known Member

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    Thanks folks.......I on the same page now..... ;)
     
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