Libre Confusion

ElyDave

Well-Known Member
Messages
2,087
Type of diabetes
Type 1
Treatment type
Insulin
I've got my annual appointment coming up, and I was going to discuss the Abbot Libre thingy now that it's potentially available on the NHS.

I'm not clear from their website though as to whether it's considered suitable for pre-meal readings to decide boluses? If so, how or if, would it interact with my pump, or would I still be needing to take finger prick readings for that?

If the latter, then I'm still going to need to take three readings a day that way, which would reduce but not eliminate the need for blood glucose strips.
 
  • Like
Reactions: novorapidboi26

Diakat

Expert
Retired Moderator
Messages
5,591
Type of diabetes
Type 1
Treatment type
Insulin
Dislikes
The smell of cigars
Abbott are clear it does not eliminate the need for test strips.
Some people are happy to bus from the Libre. I am occasionally when I have established a pattern of how far out from my finger tests it is.
 

catapillar

Well-Known Member
Messages
3,390
Type of diabetes
Type 1
Treatment type
Insulin
Abbott don't want you bolusing off libre readings, their own bolus calculator that comes in the libre reader requires a finger prick reading rather than a libre reading. It depends how much faith you have in the accuracy of the sensor as to whether you are confident to bolus off it.

The libre doesn't interact with any pump, at all.

DVLA do not recognise libre, so finger pricks are required for driving.
 

Snapsy

Well-Known Member
Messages
2,552
Type of diabetes
Type 1
Treatment type
Pump
Now I've really got to know my Libre and my pump (nearly two years and just over two years of experience, respectively) I do sometimes use flash readings for on-the-hoof correction boluses. This is my own decision and I feel confident in doing this, although I am aware that it is not recommended.

I've never used the Libre's own bolus calculator when calculating mealtime boluses, nor have I ever used it as a blood test meter - I use my pump handset for both of those jobs.

I do a lot of flash testing with my Libre, and these days I do fingerprick tests probably only 6 times a day (more if I'm using the car) rather than the 12+ tests a day I used to do pre-Libre.

:)
 

Scott-C

Well-Known Member
Messages
2,474
Type of diabetes
Type 1
I'm not clear from their website though as to whether it's considered suitable for pre-meal readings to decide boluses?

After using it for a few months, I got a sense of how close or not a particular sensor was and decided I could safely bolus from it. It's a personal judgment call.
 

ElyDave

Well-Known Member
Messages
2,087
Type of diabetes
Type 1
Treatment type
Insulin
@Snapsy 12+ tests a day before the libre :wideyed:, I'm typically 7 except when out on a long run/ride, where it's one per hour. Really that is what the libre would eliminate for me.
 

JoeT1

Well-Known Member
Messages
277
Type of diabetes
Type 1
Treatment type
Insulin
I have only used the Libre for 10 days, but I certainly would not bolus from it. The readings can be off for me up to 2-3mmol at certain times either way and that's comparing to the Libre finger prick.

By the way, does anyone also use the finger prick on the reader? Do they find that accurate or a tad high compared to other finger prick meters?
 

Diakat

Expert
Retired Moderator
Messages
5,591
Type of diabetes
Type 1
Treatment type
Insulin
Dislikes
The smell of cigars
Yes, I use it a couple of times to check the sensor against my usual meter. This one is constantly higher than my meter. But I did have one sensor that could be up or down from my usual meter by 3.
 

JoeT1

Well-Known Member
Messages
277
Type of diabetes
Type 1
Treatment type
Insulin
Yeah, so I might get a reading of

Sensor 13.8
Libee Finger Prick 13
Glucometer 12

No idea which to take
 

Diakat

Expert
Retired Moderator
Messages
5,591
Type of diabetes
Type 1
Treatment type
Insulin
Dislikes
The smell of cigars
Yeah, so I might get a reading of

Sensor 13.8
Libee Finger Prick 13
Glucometer 12

No idea which to take
I decided to stick with my meter as standard because I know my a1c is close to it. So then if the Libre is constant in difference I can mentally 'correct.
 

Snapsy

Well-Known Member
Messages
2,552
Type of diabetes
Type 1
Treatment type
Pump
@JoeT1 to put it into context, I never bolus from the Libre based on just the one reading - I need to refer to several 'bips' to check how my trend is going and how fast or slow any rise is.

It is I feel with good reason that they don't recommend bolusing using just a flash reading.

:)
 
  • Like
Reactions: JoeT1

JoeT1

Well-Known Member
Messages
277
Type of diabetes
Type 1
Treatment type
Insulin
@JoeT1 to put it into context, I never bolus from the Libre based on just the one reading - I need to refer to several 'bips' to check how my trend is going and how fast or slow any rise is.

It is I feel with good reason that they don't recommend bolusing using just a flash reading.

:)


I find that even the finger prick is always reading higher than my normal glucometer....now, which one is right you may say? I think I just need to use the Libre sensor for trends and knowing if I am rising or dropping, and if possible, finger prick with my normal meter, if out and about, I can finger prick with the Freestyle Libre finger prick, just so as to not be carrying around two meters.
 

Snapsy

Well-Known Member
Messages
2,552
Type of diabetes
Type 1
Treatment type
Pump
@Snapsy 12+ tests a day before the libre :wideyed:, I'm typically 7 except when out on a long run/ride, where it's one per hour. Really that is what the libre would eliminate for me.
To be fair, before I started pumping I would probably test 8+ times a day. I started pumping in the October before getting my Libre the following February, so my level of testing was full-on, at around the 12 mark. My record I think in that new-pump period was 20 fingerprick tests in a day.

I am, by nature, obsessive. My diabetes rules my life - I put my hands up to that!

:)
 

Snapsy

Well-Known Member
Messages
2,552
Type of diabetes
Type 1
Treatment type
Pump
I find that even the finger prick is always reading higher than my normal glucometer....now, which one is right you may say? I think I just need to use the Libre sensor for trends and knowing if I am rising or dropping, and if possible, finger prick with my normal meter, if out and about, I can finger prick with the Freestyle Libre finger prick, just so as to not be carrying around two meters.
Good point! My reader typically reads higher than my blood tests, and if I didn't know that from using it and comparing it a lot with blood tests I wouldn't dare to bolus from just the Libre data. It's idiosyncrasies do in my case seem pretty consistent!
 

Scott-C

Well-Known Member
Messages
2,474
Type of diabetes
Type 1
Yeah, so I might get a reading of

Sensor 13.8
Libee Finger Prick 13
Glucometer 12

No idea which to take


Joe, when you're in the low teens, all of those numbers are basically the same.

If I recall correctly from earlier posts, you're an engineer, so you probably expect a degree of certainty in measurements.

Precision is a relative term when it comes to measuring bg. For various biological and electro-chemical reasons, there's a lot of "wooliness" in the subject, but, once you get to grips with it, it's perfectly possible to make rational decisions about what's going on.

In an ideal world, I'd like my bg to be around 5 as often as possible, but I know that, given the amount of variables involved, that's wishful thinking, so I'm ok with it floating around between 4 to 7.

What's that got to do with libre inaccuracies? What it means is that I've got three zones I pay attention to. 4 to 7 is fine, below 4 needs attention, so does above 8. I'm not interested in the actual numbers, just generally which ballpark I'm kinda in. It's not a case of saying I'm 5.5, more 5 ish.

Big differences in libre/meter tests are important at lower numbers because of hypo risk, and I'm not going to pretend that those don't happen with libre arround the 4 to 5 mark, but when they're happening around the mid-teens, I wouldn't expect the numbers to be the same, because I don't think the libre factory calibration is based on being accurate at such high numbers.

The numbers you've given in your example, between 12 to 13.8, I would be paying absolutely no attention at all to which one is correct, because all I need to know, if I was in that situation, is that they're generally around 13, therefore too high, and none of them is in the 4 to 7 zone, I'd just be saying all of them are much higher than I'd want, so I'd be thinking about a correction dose. The 1.8 difference wouldn't make a huge amount of difference to the amount of the correction dose - that can be tweaked with a few biscuits once back in range.

How calibration works plays a major part in this. None of these things, neither dexcom nor libre, will be stable over a wide range of bg. If you use dexcom, the general advice is to calibrate while stable. If you do that while in say a 4 to 7 range, it'll be calibrated for that range, but that really doesn't mean that that calibration is going to hold true if you're floating around in a completely different range in the mid-teens.

Libre is factory calibrated. It's meant to mean it'll be accurate all the time without doing the dexcom twice a day gig but we all know that that kinda doesn't work. I'm not a scientist, so I have no idea at all about Abbott's factory processes, but I suspect that they've calibrated based on users being around 4 to 8, because that's where T1s should normally be, and not being in rhe mid-teens, so it's no surprise that there's going to be some wild flyers the further out of range you are: if it's calibrated for 4 to 7, that calibration won't work for 10 to 15, so there will be inaccuracies.

We've talked on other threads about kitting libre out with blucon to make libre a cgm. Calibration will play a part in that. The sensor is sending a number to the app and the app then turns it into a bg reading. Calibrating is taking a bg reading and telling the app my bg is x right now so when you get a number from the sensor, that's what it means in terms of actual bg. If you do that when bg is flying around all over the place, it'll get confused, and it'll also get confused if you're telling it how it looks when you're at 12.8, compared to telling it when you're at 5.6. I suspect that libre is set up to read well when in a general 4 to 7 range, but not so much when in the teens.

I'm honestly not sure whether that's made anything clearer or more complicated, but all I know is that, after a bit of experience of using these things, you can take what it's telling you, make a few adjustments to account for the inherent uncertainties of them, and then say, aye, ok, I'm now going to do x,y,z based on it, without any serious risks to health.
 
  • Like
Reactions: Diakat
D

Deleted Account

Guest
I have tried the Libre and Dexcom.
After some frustration about differences compared to finger pricking for both, I have come to the conclusion neither can replace finger pricking. That is not to say they are a waste of time or money: they are incredibly useful but not for point readings.
The value comes from history and trends. I now have a much better deal of which foods cause a spike and when they do so; I have a much better hold on when to reduce and increase my basal for different types of exercise; I have configured my basal rise to match my morning liver dump; I could go on ...
I have read posts on this forum from some people who have found the Libre very accurate, I have spoken to a mother who rarely pricks her son’s finger any more, I have spoken to sportsmen who use their Libre to highlight if they are closing in on a hypo when out running. But I have also spoken to people who have come to the same conclusion as I have.
Maybe our bodies react differently to the sensors or maybe we have different levels of trust of new tech. The choice is yours.
... unless you are driving in the UK: the choice is then the DVLA’s and they choose finger pricks.
 
  • Like
Reactions: Ledzeptt

ElyDave

Well-Known Member
Messages
2,087
Type of diabetes
Type 1
Treatment type
Insulin
That 12 or 13.8 would make a huge difference in correction dose for me. My total basal insulin on the pump is about 4 units/day and total insulin typically <7units/day. This was one of the reasons I went on the pump, much easier to manage smaller doses, particularly around sport/exercise.

Similar to Scott though, I tend to think <4 - correct, 4-6 OK, 7-8 correct at next meal, >8 correct