All FreeStyle Libre Sensors Consistently 2mmol Higher Than Finger Pricking

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othytim

othytim

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Type 1
Hallo. I've been using FreeStyle Libre 1 for some years now (I think 4ish) and have just moved over to FreeStyle Libre 2.

Every single sensor I've had that has worked properly has consistently read 2mmol higher than whatever finger prick meter test I've done at the time. I think I've had about 4 different finger prick meters over the time.

I'm just wondering if this happens with others? Maybe this is a common phenomenon?

It basically means that if my FreeStyle Libre says I'm 5.8, I know that in reality I'm about 3.8. I tend to use xDrip+ (which can be calibrated) with a Miaomiao1 to get around this problem, but still scan the sensor to keep the NHS happy.

Yeah, so does anyone else get this? Oh, and this has nothing to do with the delay between finger prick readings and interstitial fluid etc.

Thanks, Tim
Oh and I'm Type 1.
 
othytim said:
Hallo. I've been using FreeStyle Libre 1 for some years now (I think 4ish) and have just moved over to FreeStyle Libre 2.

Every single sensor I've had that has worked properly has consistently read 2mmol higher than whatever finger prick meter test I've done at the time. I think I've had about 4 different finger prick meters over the time.

I'm just wondering if this happens with others? Maybe this is a common phenomenon?

It basically means that if my FreeStyle Libre says I'm 5.8, I know that in reality I'm about 3.8. I tend to use xDrip+ (which can be calibrated) with a Miaomiao1 to get around this problem, but still scan the sensor to keep the NHS happy.

Yeah, so does anyone else get this? Oh, and this has nothing to do with the delay between finger prick readings and interstitial fluid etc.

Thanks, Tim
Oh and I'm Type 1.
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Hello @othytim, 5 years using Libre, mine are sometimes higher, sometimes lower; and like you I use xDrip+ on android to give a better result.
 
Benny G said:
Hello @othytim, 5 years using Libre, mine are sometimes higher, sometimes lower; and like you I use xDrip+ on android to give a better result.
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Hi Benny. Thanks for your reply. When yours are higher/lower, is it by a similar degree, like 2mmols? Sounds like it's not so consistent for you then! Tim
 
Not consistent, I have had the odd sensor be out by 4 or 5 mmol, but worked OK with xDrip. I find that my sensors are as likely to be a little high, as they are to be a little low.

If your sensors are consistently reading 2 mmol higher I cannot provide an explanation. Spooky.
 
Yes yes and yes. I’ve complained about this many times on here. I’ve kinda got used to it now, wish there was some way to calibrate. See when your in the teens and moving quick you accept a couple of points but if my sensor says 8, even when I’m steady for hours finger will be 6. Dexcom didn't do this but can’t get a script for that. Only thing is when the DN checks from her end it’s not a true reflection

And yes with mine it’s consistent… always been that way
 
EmmaL76 said:
Yes yes and yes. I’ve complained about this many times on here. I’ve kinda got used to it now, wish there was some way to calibrate. See when your in the teens and moving quick you accept a couple of points but if my sensor says 8, even when I’m steady for hours finger will be 6. Dexcom didn't do this but can’t get a script for that. Only thing is when the DN checks from her end it’s not a true reflection

And yes with mine it’s consistent… always been that way
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wish there was some way to calibrate

OP and myself both calibrate with xDrip+, there are several 3rd party options. I think you mean you would prefer a calibration feature built into Libreview; I would prefer that too.

@EmmaL76, 2 mmol higher consistently is spooky for you as well. If there are two of you, surely there must be more.
 
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I am still on Libre 1 and reluctant to change because it works really well for me and is usually pretty consistently 0.5 to 1mmol lower than a finger prick in range. Sometimes when I first start a new sensor up (even when it has been applied 24hrs in advance) it will read a little higher than finger prick (sometimes 1-2 mmols) for the first half/day which really throws me but then settles down to the usual slightly lower reading. Unfortunately this means that it shows me in the red much more than I actually have been but my consultant knows the score and is cool with it.
I am quite surprised that you find Libre reads higher than actual finger pricks because I thought most people found it read lower like myself. Of course at higher levels like mid teens it usually reads higher which I accept but in range or low and it leans towards lower numbers. I actually thought this was a built in safety feature in some respects to give people more time to respond to hypos.
 
rebrascora said:
I am still on Libre 1 and reluctant to change because it works really well for me and is usually pretty consistently 0.5 to 1mmol lower than a finger prick in range.
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I'm still finding that's about right with Libre 2. Now and again (especially when BG is changing quickly (but not so quickly that it says the reading is unavailable and I should scan again in 10 minutes)) it shows a figure that later disappears (and doesn't appear on the graph). My guess is that's the prediction algorithm getting its prediction slightly wrong; I'm not sure whether that's specific to Libre 2 or not.

I don't remember any sensor consistently reading higher. But people are different, so maybe some people's interstitial fluid reacts a little more strongly with whatever the sensor is measuring.
 
Like others on here, my Libre 1 sensors sometimes read higher and sometimes lower than a finger-prick test. I've just learned to calibrate with xDrip as best I can, though that can be challenging at times. Quite frustrating really, but add it to the list of oddities this condition brings with it, I guess. :(
 
Like Benny been using libre for around 5 years.

Had issues with libre 1 which took while to figure out, it turned out it was old version of software & once updated all was good.

Switched to libre 2 when it became available here, vast improvement on 1 not just because addition of low/high bg alarms just find it more accurate with bg reading even at high & low levels.

When having issues with libre 1 consultant did warn me that libre doesn't work for everyone, probably thinking at time I was one with readings that were constantly out, so maybe your just one of those unlucky ones who knows.
 
I am not a Libra user or a T1, just an old scientist who used to measure stuff for a living and still gets into measuring stuff as a hobby. That said, to get Libra and Finger pricks to get readings within two units of each other is technically amazing.

They measure different things in different parts of the body and by some sort of wizardry (can guess what it might be) each method gets numbers that are close to that you might get from a proper blood sample. As I have said before, you can round the reading on a blood glucose meter to the nearest whole number and then add an error of +/- 1 unit. Cannot give any information for the Libra but I would suspect the reproducibility would be worse because of the added step of making a correction due to measuring interstitial fluid and not blood. From that I would expect reasonable correlation between libra but not be surprised if they were three or even more units different.

By the way, you cannot calibrate a Libra against a hand held monitor simply because of the error intrinsic in its method of operation.

All that said, the technology is amazing, the fact that the kit can get anywhere near what you would get from a blood sample is quite remarkable. My advice to anybody is to recognise the foibles of the technology you are using and use it in a way that suits you. The numbers you get from Libra and hand held monitors are far better than what you can get by any other means but they are best thought of as indicators and not absolute values.
 
I completely agree that Libre, for all its foibles, is still an amazing device. I never expect the Libre value to exactly match a finger test. I carry a Contour Next meter with me when I'm out and about and I know from experience that it will never exactly match the Freestyle meter, so I don't worry too much about whether the value is out, as long as it's close. For me, it's the early warning of up and down trends that is important. For that, the xDrip alerts I've set up help me immensely.
 
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