Libre readings differing from meter readings, why??

[Jellytots]

Hi all, I've been on my libre for 24hrs now and noticed that my readings are differing with every test. My last libre scan was 11.7 yet my meter was giving me a reading of 9.2. My sensor is in my arm as recommended. Is anyone else having readings differ this much? As I'm new to it I'm not sure what's normal or not!

 

[novorapidboi26]

That is normal........as the Libre is reading interstitial fluid and not blood there is a delay....

there are also many other uncontrollable factors unique to each individual which can knock out the reading further or closer to that of the blood....

 

[Deleted Account]

To add to the points @novorapidboi26 mentions, many people find the variation is small and consistent for a sensor. They just learn to calculate the difference for each sensor and add or subtract this amount each time.
Some people (including me, unfortunately), find there is no logic or consistency. About all I could say is that my Libre readings go up and down at approximately the right time.
This may be because my BG changes pretty fast so the 15 - 20 minute delay is very noticeable.

@Jellytots just out of interest, is your Libre prescribed or self-funded?
I ask because I believe there is a lot of value to be obtained from the Libre but only if you know how to use it so it needs some training rather than the NHS just handing them out and expect people to work it out themselves.

Finally, I love that both of you have cute dogs

 

[Antje77]

I agree with the above and would like to add that the libre might give off results in the first 24 hours after inserting. I usually insert a new sensor about a day before the old one has ended, and only activate when the old one has finished. The 14 day countdown only starts after activating, so you won't lose any days.

 

[therower]

Hi @Jellytots . Welcome to the forum. Not a libre user myself , I use dexcom, but the two are alike in that they need time to settle down after application. After all you are implanting a foreign body into your body. The bodies defence system reacts to this initial invasion, this reaction can give wayward readings within the first 24 hrs.
Good luck with the libre.

 

[Gates]

8.3 at 4:00pm a bit better result, well in fact a brilliant result compared to a couple of months back and for the previous 12 months. I had finished with a specialist dietician whom had tremendous patience with me. My Drugs had been increased for pain which had such an effect on me although I did not think so. The time was extremely strange, nevertheless just getting somewhere and my Dr whom I have dealt with for the last 8years has up and left the surgery, an appointment Monday afternoon for me to meet the new designated Dr. I have met her before, but some time back.

 

[videoman]

Having used the Libre on a trial ,I tested my blood and got a reading about 4 points different. However to if you check two blood meters using the same sample on to the senser you will find that two meters with the same sample will give you different read

 

[barrym]

There's stacks on this subject here, so if you want to read it all get searching. But in reality consider this. 1, why do you consider the meter to be gospel? Lots of potential variation there too. 2. What would you do differently from those two readings? Not much I imagine.

I think it must be intentional that the libre tends to be closer to a meter, or the other way round, when you are at 4 or 5, and as you go lower the libre goes lower quicker, one as you go higher the libre goes higher more quickly too. I think this is done in the software intentionally to give you a heads up early. There are other apps that scan the libre that give much closer readings.

Check it all out and I reckon you'll see it for what it is and like it for that.

 

[Jellytots]

To add to the points @novorapidboi26 mentions, many people find the variation is small and consistent for a sensor. They just learn to calculate the difference for each sensor and add or subtract this amount each time.
Some people (including me, unfortunately), find there is no logic or consistency. About all I could say is that my Libre readings go up and down at approximately the right time.
This may be because my BG changes pretty fast so the 15 - 20 minute delay is very noticeable.

@Jellytots just out of interest, is your Libre prescribed or self-funded?
I ask because I believe there is a lot of value to be obtained from the Libre but only if you know how to use it so it needs some training rather than the NHS just handing them out and expect people to work it out themselves.

Finally, I love that both of you have cute dogs

Thanks for your input... My sensors are self funded. Firstly I love the tech behind them and second, I wanted to know what my Bg is doing when I'm not testing. Turns out I seem to have good numbers when I test, but the in between is a little out of whack. I've got a fair bit of homework to do regarding bolus lengths it seems...

And the pooch is Alf, my Greyhound ️ I also think he's the most adorable boy in the world my husband has always come second to him!! (and he knows it haha) now he's further down the list as we have a girly hound too and a daughter also

 

[Jellytots]

I agree with the above and would like to add that the libre might give off results in the first 24 hours after inserting. I usually insert a new sensor about a day before the old one has ended, and only activate when the old one has finished. The 14 day countdown only starts after activating, so you won't lose any days.

I've also read this somewhere else, it's a good tip to try with my next sensor, thank you!

 

[Jellytots]

There's stacks on this subject here, so if you want to read it all get searching. But in reality consider this. 1, why do you consider the meter to be gospel? Lots of potential variation there too. 2. What would you do differently from those two readings? Not much I imagine.

I think it must be intentional that the libre tends to be closer to a meter, or the other way round, when you are at 4 or 5, and as you go lower the libre goes lower quicker, one as you go higher the libre goes higher more quickly too. I think this is done in the software intentionally to give you a heads up early. There are other apps that scan the libre that give much closer readings.

Check it all out and I reckon you'll see it for what it is and like it for that.

You make some valid points, thanks for your insight. I suppose out of the two readings I'd be more likely to favour the lower of the two! Now you've pointed out how the libre appears to go lower/higher quicker, I've noticed this too. I'll definately read up on the info on here, I'm sure I'll pick it up fairly quickly once I get my head around it all. Thanks again!

 

[Scott-C]

Hi, @Jellytots , there's a paper at the link below which discusses the relationship between blood glucose and interstitial fluid glucose.

I read it shortly after I got libre, and it helped a lot figuring out what was going on, even though most of the science stuff is waaay over my head.

www.ncbi.nlm.nih.gov/pmc/articles/PMC2903977/

 

[Jellytots]

Hi, @Jellytots , there's a paper at the link below which discusses the relationship between blood glucose and interstitial fluid glucose.

I read it shortly after I got libre, and it helped a lot figuring out what was going on, even though most of the science stuff is waaay over my head.

www.ncbi.nlm.nih.gov/pmc/articles/PMC2903977/

Great thanks, I'll have a read of this tonight

 

[Scott-C]

Great thanks, I'll have a read of this tonight

Forgot to mention, if you've got a Kindle handy, there's a couple of books on getting the most out of cgm:

Sugar Surfing - Stephen Ponder
Beyond Fingersticks - William Lee Dubois

Dubois is a bit dated now, but still makes a lot of good points.

Libre's definitely got a few quirks, so what I did in the first week or two was test a lot more than I normally did, about 10 to 15 times a day, so I could get a better idea of how it worked in relation to blood in different situations.

Sure, that was a lot of testing, but it paid off as it got me to the stage after a while where I'd just do a couple of calibration checks each day, so ended up being ok with bolusing from it, but that's always going to be a personal judgment call.

Have fun with it - it's a brave new world!

 

[Jellytots]

Forgot to mention, if you've got a Kindle handy, there's a couple of books on getting the most out of cgm:

Sugar Surfing - Stephen Ponder
Beyond Fingersticks - William Lee Dubois

Dubois is a bit dated now, but still makes a lot of good points.

Libre's definitely got a few quirks, so what I did in the first week or two was test a lot more than I normally did, about 10 to 15 times a day, so I could get a better idea of how it worked in relation to blood in different situations.

Sure, that was a lot of testing, but it paid off as it got me to the stage after a while where I'd just do a couple of calibration checks each day, so ended up being ok with bolusing from it, but that's always going to be a personal judgment call.

Have fun with it - it's a brave new world!

Yeah I'll happily give anything a read if it will help. I only have Pumping Insulin to help but obviously that's not CGM focused etc. Thank you