Could my sensor be faulty

[Alineden]

Hi.

I have type 2 and every once in a while I buy a couple of Freestyle Libre sensors and use them to monitor what foods are doing what to my BG levels. Also if my diet hasn't been too good I find that seeing my levels helps keep me honest with myself.

I have just started wearing a new sensor and although I've been eating well I've been surprised at how low my BG appears to be.

The fist photo is of the last 24 hours. The second one is a typical day from a previous sensor. On the second one, meal times and getting ready to wake up are clearly visible but on the first there is very little change.

Do you think I could have a faulty sensor?

Thanks

Alan

 

[Rokaab]

Do you think I could have a faulty sensor?

If you are not sure about it then the only way to tell is to do a blood test to verify whether its right or wrong I'm afraid, no other way to tell.
If your diet has changed a lot (to a diet that your body can cope with) from the first sensor that may explain it, but a blood test is the only way to check

 

[EllieM]

Entirely possible if you've recently adopted a low carb diet, which is now paying off. But, do you have access to a blood testing meter. Libres can be notoriously unreliable and you really need a meter to check its accuracy.

 

[xfieldok]

The libre needs a good 8 hours to bed in before you use it. My libre failed during the night and I had to slap a new one on this morning. I started to scan straight away but expect the numbers to be a bit wobbly until this evening.

 

[Jaylee]

Hi.

I have type 2 and every once in a while I buy a couple of Freestyle Libre sensors and use them to monitor what foods are doing what to my BG levels. Also if my diet hasn't been too good I find that seeing my levels helps keep me honest with myself.

I have just started wearing a new sensor and although I've been eating well I've been surprised at how low my BG appears to be.

The fist photo is of the last 24 hours. The second one is a typical day from a previous sensor. On the second one, meal times and getting ready to wake up are clearly visible but on the first there is very little change.

Do you think I could have a faulty sensor?

Thanks

AlanView attachment 42709View attachment 42710

I would agree regarding checking against the meter..

But there are a couple pretty good, free 3rd party apps which allow calibration with your meter. Which can close the gaps on any discrepancy twix the two.. Though it won't smooth it out if the sensor goes a bit scatty whilst bedding in or sometimes at the end of sensor life..
I find making sure I'm hydrated helps too?

 

[Alineden]

OK so took a reading from the FS Libra followed by one with the SD Code Free then another with the SD Code Free. All of them within a minute or so of each other.

 

[Goonergal]

Libre sensors can run lower or higher than finger pricks. For a period mine always ran low. The last few have run high compared to finger pricks. I’d only regard a sensor as faulty if it was giving inconsistent results - e.g. sharp fluctuations not matched by finger pricks. If it’s consistently either higher or lower than finger pricks I don’t worry about it as I’m looking for trends.

 

[Jaylee]

OK so took a reading from the FS Libra followed by one with the SD Code Free then another with the SD Code Free. All of them within a minute or so of each other.View attachment 42715View attachment 42716View attachment 42717

Hi,

What i find after calibrating my CGM set up with the Libre, MM2 & xdrip app.is any checks with my meter on the flat, i count back 15 or 20 minutes 3 or four dots back (It automatically scans & sends to my phone every 5 mins.)
For some reason, it seems to track me quicker going down but slower than my meter coming up out of a low. (i'm fully hypo aware.) i can get my cognitive back & the meter agrees. But there can be a little lag with the xdrip graph.. All in all if itlooks within 0.4 of my meter on xdrip, then no worries on the flat..

 

[EllieM]

The libre has a lag time of 15 minutes relative to your meter, so you need to do a blood test and then check the libre 15 minutes later.

 

[Jaylee]

The libre has a lag time of 15 minutes relative to your meter, so you need to do a blood test and then check the libre 15 minutes later.

Enough time to soak a Frio wallet? Seriously, the the periodic representation every 5minutes on XDrip means one can test, tap on the dot in that period of lin ear time & the BG in that point flashes up in the bottom left hand corner of the device. (With the time it was relayed.) No vauge markers like on a Libre app.

"Great Scot!" I'm sounding like that Doc out of Back to the future..

 

[EllieM]

Seriously, the the periodic representation every 5minutes on XDrip means one can test, tap on the dot in that period of lin ear time & the BG in that point flashes up in the bottom left hand corner of the device. (With the time it was relayed.) No vauge markers like on a Libre app.

Still confused by this. Given that the libre interstitial reading lags behind your blood sugar readings, how does the xdrip know what the libre is going to read in 15 minutes, when it catches up with the blood test just performed...? Or does it predict blood sugars ahead? (Fine if you are flat,, not so good if you are hypo.) Does it incorporate the interstitial delay into its graphical representation?

Mind you, the terminology is a bit confusing here. Maybe we should use BG for blood glucose readings and IG for interstitial readings (eg libre or dexcom).

I suspect I am misunderstanding something fundamental here, my apologies for the questions. (Not an xdrip user as I am too allergic to the libre for its readings to be anything other than wildly inaccurate, in both directions, for me.) Though I have recently started using a dexcom, which does have the dot every 5 minutes.

 

[Jaylee]

Still confused by this. Given that the libre interstitial reading lags behind your blood sugar readings, how does the xdrip know what the libre is going to read in 15 minutes, when it catches up with the blood test just performed...? Or does it predict blood sugars ahead? (Fine if you are flat,, not so good if you are hypo.) Does it incorporate the interstitial delay into its graphical representation?

Mind you, the terminology is a bit confusing here. Maybe we should use BG for blood glucose readings and IG for interstitial readings (eg libre or dexcom).

I suspect I am misunderstanding something fundamental here, my apologies for the questions. (Not an xdrip user as I am too allergic to the libre for its readings to be anything other than wildly inaccurate, in both directions, for me.) Though I have recently started using a dexcom, which does have the dot every 5 minutes.

Hi,

It's late here in the UK. (2am.)
& i'm certainly not contesting your view.
Meters have a lag during hypos? Which is why folk panic treating then ask why "nothing's working." Then find later, they have shot up & over treated?
But in my experience with the libre. Meters do have a lag & still consistently lag behind libre readings on the CGM set up by at least 15 minutes? Unless there is a rise from a low in which case an interstitial reading from a libre in my experience at least Lags behind the meter & how I feel as hypo awair? (Ironically, by another 20 minutes..)
With me my meter & how I feel regarding "out of the woods" with a low? Corresponds, but the Libre hangs back.. Untill I level out. Calibrated, levels & climbs from normal parameters correspond, but sub 3.5 lows interpret as a little sketchy? Coming back up..

In short, the set up is great a telling me where I am at deviations out of normal parameters but a little slow even slower than my meter registering coming up off sub 4mmol.?

 

[Alineden]

Can anyone explain why the finger price test results using the SD Code Free varied from 8.7mmol/L to 7.5mmol/L when taken one minute apart. Is this the level of inaccuracy that is to be expected?

 

[KK123]

Can anyone explain why the finger price test results using the SD Code Free varied from 8.7mmol/L to 7.5mmol/L when taken one minute apart. Is this the level of inaccuracy that is to be expected?

In a word, yes. That is about as accurate as they are going to get (don't ask me why, I'm sure there is some technical reason). I think that if it's within 1.5mml of the tested solution range then it's 'working'. I use the libre and although I love it, it does worry me that I am having to use it for insulin injections when so many people are saying it reads higher or lower than a glucose meter might. I do have some strips to test with should it throw up a very unexpected result but the strips are now restricted so I'm relying solely on the Libre as instructed by my Diabetes team.

 

[KK123]

Libre sensors can run lower or higher than finger pricks. For a period mine always ran low. The last few have run high compared to finger pricks. I’d only regard a sensor as faulty if it was giving inconsistent results - e.g. sharp fluctuations not matched by finger pricks. If it’s consistently either higher or lower than finger pricks I don’t worry about it as I’m looking for trends.

Hi Goonergal, we all use it in different circumstances obviously but I wish they would find a way to improve its accuracy as the trend (which is massively useful) isn't so great when I'm having to decide on how many units of insulin to inject. Having said that, even when on finger pricks I would have to rely on ONE random reading to determine dosage so I guess it's swings & roundabouts. x

 

[EllieM]

Can anyone explain why the finger price test results using the SD Code Free varied from 8.7mmol/L to 7.5mmol/L when taken one minute apart. Is this the level of inaccuracy that is to be expected?

I think so. As I remember (possibly incorrectly) the SD isn't renowned for accuracy, just for cheapness....

 

[KK123]

I think so. As I remember (possibly incorrectly) the SD isn't renowned for accuracy, just for cheapness....

I agree with Ellie but I have used at least 5 monitors over the last 3 years from cheap to very expensive & all brands and found they ALL can be 1 to 1.5mmols 'out' as it were even when using the same drop of blood across each or seconds apart, etc, etc.