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Difference in readings

PatsyB

PatsyB

Well-Known Member
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3,054
Location
Notts
Type of diabetes
Type 2
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Insulin
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Diabetes
I had a sensor fitted last week which after two days fell off however had another delivered which I put on , I am finding the reading differ to what my finger prick does has everyone else on a sensor noted this?
this morning when I got up finger prick said 4.9 my sensor said 7.3??
 
I think there is a lag in the sensor reading @PatsyB , from what I have read (don't use one, myself)

Think the range I heard of is 15 minutes ?
 
Hi @PatsyB they do generally differ yes, as Libre reads interstitial fluid and glucose monitors read actual blood. The beauty of Libre is the arrows and trends. Very important for people on insulin. Did you check the Libre reading 10 mins later to see if the levels had risen to nearer the blood reading. I often find that happens as Libre is behind. The difference you quote is not far from the accepted 2mmol. I have various glucose monitors I’ve collected over the years and have tested 2 at a time in the past and even they differ. In reality it is not an exact science.
 
jjraak said:
I think there is a lag in the sensor reading @PatsyB , from what I have read (don't use one, myself)

Think the range I heard of is 15 minutes ?
Click to expand...
There is a delay between blood sugar readings and interstitial fluid readings. However, there is NO delay between the blood sugar readings reported by Libre.
This is because the algorithm Libre uses to calculate blood sugar based on interstitial fluid takes the delay into account
As a user of Libre (and other CGMs) it is frustrating to read these myths perpetuated to people who are new to them.

To get the most out of Libre, you need to understand the limitations which does not include this delay.
It is the bedding in period
It is the calibration at "normal" levels
It is compression lows.
 
In Response said:
There is a delay between blood sugar readings and interstitial fluid readings. However, there is NO delay between the blood sugar readings reported by Libre.
This is because the algorithm Libre uses to calculate blood sugar based on interstitial fluid takes the delay into account
As a user of Libre (and other CGMs) it is frustrating to read these myths perpetuated to people who are new to them.

To get the most out of Libre, you need to understand the limitations which does not include this delay.
It is the bedding in period
It is the calibration at "normal" levels
It is compression lows.
Click to expand...
Are there different ‘versions’ of the libre 2 sensor or app? I ask only because the instructions that came with my libre 2 specifically mention the lag and even has a nice diagram of 2 cars driving up and down a hill (representing BGL) with the behind car 10 minutes behind. I’ve read somewhere — I think the juggluco docs — that there’s EU and American versions of the libre 2 sensor but have no idea what the difference is

edited to add: in Australia I think we have the USA ‘version’ which might be the reason for the lag diagram using cars to illustrate?
 
PatsyB said:
I had a sensor fitted last week which after two days fell off however had another delivered which I put on , I am finding the reading differ to what my finger prick does has everyone else on a sensor noted this?
this morning when I got up finger prick said 4.9 my sensor said 7.3??
Click to expand...
Hi @PatsyB ,

Looking at your Libre graph. (The time whilst asleep & before the finger prick & scan.) Is the line flat’s around “7.3.” Or is it more a jump from a lower reading around 5mmol?
 
In Response said:
There is a delay between blood sugar readings and interstitial fluid readings. However, there is NO delay between the blood sugar readings reported by Libre.
This is because the algorithm Libre uses to calculate blood sugar based on interstitial fluid takes the delay into account
As a user of Libre (and other CGMs) it is frustrating to read these myths perpetuated to people who are new to them.

To get the most out of Libre, you need to understand the limitations which does not include this delay.
It is the bedding in period
It is the calibration at "normal" levels
It is compression lows.
Click to expand...
Mmhh

My post says "I think" ...used to suggest there might be a reason.

The finger test doesn't seem to have the same 'limitation' issues the CGM's seem to have ?

I'd say my post was reasonable to a new user perhaps concerned the readings were different.

Perhaps you can explain a little more just why the CGM reading was so far above the finger test.

If I was using one, and had concerns to accuracy I think I'd definitely defer to the finger test reading.

Cheers for the post though
Always good to be informed of improving technology.
 
HSSS said:
Was that an upgrade between the original and libre 2?
Click to expand...
Possibly.
I started using Libre 2 so long ago that I forget.
However, it would only be a software change on the app/reader.
Other CGMs do something similar so the delay is pretty irrelevant now.
 
In Response said:
Possibly.
I started using Libre 2 so long ago that I forget.
However, it would only be a software change on the app/reader.
Other CGMs do something similar so the delay is pretty irrelevant now.
Click to expand...
It must have been back in 2020.? (There was a log wait for it in the UK for it. Like the L3 now. Germany seems to get this stuff first.. I was self funding back then was alerted to availability by Asda pharmacy.tried it once. (& also surprised It wasn’t on prescription for me.)The L2 Non compatible with the tech I was using at the time. Went back to L1.
Then prescribed L2 by endo convinced by improvement on A1c.
Then invested in new tech to accommodate when prescribed.. I needed a new phone anyway, due to glitches & overheating. (Full of builders dust. The out door job I had at the time.)

Remember it reasonably well.
 
@PatsyB Did you check the graph from the Logbook screen on the App later? You will often find that the readings do not match where your levels really were, with the 15 min recalculation then included. If I have a random number I think is unlikely to be correct, often on first waking, if you scan again and look at the graph at least 30 mins later you will often see the possible spike has gone - the logbook will clearly show where the reading 'dot' is not on the line.
IMG_4641.jpeg
Hope this makes sense. On the graph above you can see I didn't even bother checking again for hours as I was busy and knew it was wrong, (and only 7.1!).

Also first 24-48hrs of a new sensor can be a little more erratic, which is why a lot of us put on the next sensor a day or so before activating (wearing 2) to try and negate, but I have found when I have had to do a quick swap after a failure it doesn't make that much difference, but it does mean I am ready to go if I am not conveniently at home, or forget when the old one expires.
 
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