# New to Libre 2 -mismatch with finger prick BG



## Andywidd (Jul 21, 2021)

Hi,
Just been fitted with a Libre 2 sensor today. The reading don’t seem to match my BG finger prick readings by quite a way. I had a low BG warning, scanned at 4.4 then did a finger prick (FP) and it was 3.6. Similarly later on, before tea I did a FP=4.5 but Libre was 6.3 at exactly the same time. I wasn’t expecting an exact match but this seems quite a difference? Over the last few days prior to getting the Libre  I have had a few hypo readings with no symptoms- 2.8 on Saturday from FP reading. I’m just wondering if the actual GlucoMen FP meter is incorrect and not the Libre as previously when I get to low 4,s I got a little shaky. I was only diagnosed type 1 one month ago so not sure whether to trust Libre or GlucoMen reader due to recent low readings with no symptoms. Previous to this weekend I’d only had one low 4 reading so havent had much experience of ‘feeling low’
Any advice will be greatly accepted. Cheers, Andy


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## helli (Jul 21, 2021)

Many of us find the Libre inaccurate for the first 24 ton48 hours after inserting. This is due to our bodies getting used to a foreign object inserted in our arms.
I always insert my sensor 2 days before activating it to over come this.
We are all different so some people do not need this “soak time”.

The other thing to remember is that the interstitial fluid reading is 15 minutes behind the finger prick reading. Abbott use an algorithm which attempts to accommodate this lag but only through some estimation.
Therefore, the readings are less accurate when rising or falling.


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## Andywidd (Jul 21, 2021)

Thank you Helli. I’m hoping it will reduce the finger pricks! Do you still do as many finger pricks? Or do you get to rely on your trend from the Libre and test now and again? Thanks again


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## helli (Jul 21, 2021)

Andywidd said:


> Thank you Helli. I’m hoping it will reduce the finger pricks! Do you still do as many finger pricks? Or do you get to rely on your trend from the Libre and test now and again? Thanks again


I finger prick first thing in the morning and last thing at night to check the sensor has not drifted.
Apart from that, I finger prick before correcting (Libre is not great when high or low) and if I don’t feel the same as the Libre says.
This sounds like a lot but usually it is only twice per day and I can rely on the Libre the rest of the time.

But, if you are only using Libre to cut down on finger pricks, you are only using a small amount of the power of the data you now have.
I compare it to having a smart phone and only using it to make phone calls.


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## Ljc (Jul 22, 2021)

I am using the previous version of the Libre , it doesn’t alarm , the Libre 2 that you have is supposed to be more accurate from the outset but as has already been said it’s sampling different fluid and it takes longer for the glucose to reach and then leave this interstitial fluid .

If you go into the settings you should be able to alter the BG level at which  it alerts you.

I’ve often found that the sensors become more accurate compared to a fp after a day or two .
Some here and me included at one time . Apply a new sensor without activating it a day or two before the old one runs out . You could try this with your next one .

Personally I am happy so long as mine are no more than 2 mmol/l out and it consistent in reading above or below , so until I am happy with it I don’t rely on it for blousing and never for treating hypo’s or hypers as they are less accurate when high or low.

My previous sensor was way out so I reported it to Abbott , who replaced it they requested the old sensor back, for  testing for which they sent a pre paid envelope for.

It has cut down on the number of fp I do but I find the other info it give compared to a glucose meter Much more helpful.
 The direction arrows help me decide if I need to treat that scanned 4.5 or not , ie a straight up arrow and I wouldn’t be scrabbling to get my hypo treatment ready , whereas a 5.0 with a straight down arrow I would .
The graph  helps me see what has happened when and helps me make informed choices about things like if I need to split my bolus for that meal or not , when I need to bolus as the advised 10 /15 minutes  before eating is not always right, Their was a time when I needed to bolus 50 minutes before brekkie else I spike too high , a glucose meter would not have shown me that .
It is also a great help when doing Basal checks, now that really dies cut down in the fp required and also needing to set alarms to test during g the night .

I do hope you find the Libre helpful .


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## SB2015 (Jul 22, 2021)

Hi @Andywidd 

I am another one who puts sensors in 24 hours before I need to activate it.  I seem to need a settling in time to get it to work well from day one.

The time lag between sensor readings and BG takes a bit of getting used to.  It certainly reduces finger pricks but I still use these for meal times (partly because my pump wants a Regular callibration and also habit).

The biggest benefit of sensors is the trend lines with any reading showing where you are heading, especially during exercise.  Looking back at the graphs also help when working out what foods spike you and if you want to make adjustments to the timing of your boluses.

I hope you get on well with the sensors.


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## Paulbreen (Jul 22, 2021)

I don’t seem to have to do the “soak” others do and I’m pretty aware the sensor readings are out by 1-2 units but I’m happy with them in general, I don’t remember the last time I pricked my finger (it was a pet hate after 30+ years of doing it) best advice is not to compare apples with pears as the finger prick and the sensor measure completely different fluids. The only time I may consider a finger prick would be if I’m feeling out of sorts. Having my graph in the green most of the time is all I look for and I know I’m pretty ok


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## everydayupsanddowns (Jul 23, 2021)

Hope you find the Libre provides you with data that really helps @Andywidd 

The lag for interstitial sensors can be frustrating at times, particularly where BGs are being a bit wobbly (which is just when you could really do with information you can trust!) - but all sensors and CGM share the same challenges.

Plus of course, as you point out, BG fingerstick meters have their own margins of error, and may not necessarily be ‘right’. 

As always with glucose monitoring it is important to cross-check or recheck if any result seems unusual, or doesn’t match how you are feeling. 

Let us know how you get on, and steer clear of those door frames!


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## Andywidd (Jul 24, 2021)

SB2015 said:


> Hi @Andywidd
> 
> I am another one who puts sensors in 24 hours before I need to activate it.  I seem to need a settling in time to get it to work well from day one.
> 
> ...


Cheers! This sight is great. I appreciate everyone taking the time to reply to what are, no doubt, basic questions. Very reassuring. I’ve been on 1unit fast insulin for last couple of weeks and 5 slow. I’ve just started exercise this morning(gardening) and didn’t take any insulin before breakfast. According to Libre my BG peaked briefly at 9.2 then 30mins later was down to 5.8 when I had an apple as I assumed actual BG would be lower then did another 30 mins of gardening when I peaked at 9.7 then 15 mins later was down to 4.9 on the sensor. Stopped and had 20g carb snack. I’m just learning but are these fluctuations much to worry about as normally I do quite intense exercise but can’t at moment as same time as diabetes diagnosis got full on pins and needles when I try to run! Thanks again


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## Andywidd (Jul 24, 2021)

Ljc said:


> I am using the previous version of the Libre , it doesn’t alarm , the Libre 2 that you have is supposed to be more accurate from the outset but as has already been said it’s sampling different fluid and it takes longer for the glucose to reach and then leave this interstitial fluid .
> 
> If you go into the settings you should be able to alter the BG level at which  it alerts you.
> 
> ...


Thanks for the detailed reply Lin. That is really useful to me as someone new to type 1 and new to sensors. I’ll apply the next sensor a day before I need it. My current sensor is closer to BG than it was so starting to get the feel of what I need to do (I think!).


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## Andywidd (Jul 24, 2021)

Paulbreen said:


> I don’t seem to have to do the “soak” others do and I’m pretty aware the sensor readings are out by 1-2 units but I’m happy with them in general, I don’t remember the last time I pricked my finger (it was a pet hate after 30+ years of doing it) best advice is not to compare apples with pears as the finger prick and the sensor measure completely different fluids. The only time I may consider a finger prick would be if I’m feeling out of sorts. Having my graph in the green most of the time is all I look for and I know I’m pretty ok


Thanks Paul. I haven’t been told what range I should be aiming for. I’m thinking 4-8 but is this unrealistic? Currently I’m between 3.4 and 10 with the highs and lows being very short (about 10-15mins). I was only diagnosed end of June so really just finding my feet and feel very fortunate to get a sensor(due to job necessity).


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## Andywidd (Jul 24, 2021)

everydayupsanddowns said:


> Hope you find the Libre provides you with data that really helps @Andywidd
> 
> The lag for interstitial sensors can be frustrating at times, particularly where BGs are being a bit wobbly (which is just when you could really do with information you can trust!) - but all sensors and CGM share the same challenges.
> 
> ...


Haha! I’ve just worked out the door frame joke! Can’t blame a low BG! Just a bit slow generally!


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## Paulbreen (Jul 25, 2021)

Andywidd said:


> Thanks Paul. I haven’t been told what range I should be aiming for. I’m thinking 4-8 but is this unrealistic? Currently I’m between 3.4 and 10 with the highs and lows being very short (about 10-15mins). I was only diagnosed end of June so really just finding my feet and feel very fortunate to get a sensor(due to job necessity).


Hi Andy I would say try to keep above 3.8, that’s the hypo level, 4.5>10 is a pretty nice range to be in, bit like juggling a dozen raw eggs though. Your team will try keeping you tight as possible in the early days but as you find your own way they will be more than happy to see your hab1c nice and low and steady, your body sort of lets you know if your doing the right thing


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