Bit of a difference between Shuggah and Libre readings

I’ve been using Shuggah since the problems with Librelink last weekend. My readings are maximum of 0.5 mmols/l difference. Enjoy your cake!

I’ve got Shuggah on my Apple Watch as a ‘complication’ on my watch face, so just one tap on the Shuggah icon and I get a live reading.

Chevyjay said:

Yes that’s what I have, but I saw a post last week and someone had a little icon on their Minnie Mouse face with the reading showing without touching the face which I can’t seem to get ‍ technology lol

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Oh I see, I haven’t managed to do that either!

The apps take the raw data from the sensor the run correction algorithms that are meant to correct for the changes as the sensor ages

The algorithm in different apps has been tweaked in an effort to make the reading more accurate

Some apps like xdrip on Android actually allow you to calibrate as well

But as I’ve said many times the idea of these fcgm sensors is to give reading that are in the right ‘ballpark’

The libre instruction used to state ‘not to be used for treatment decisions’ not sure if the still say that.

searley said:

The libre instruction used to state ‘not to be used for treatment decisions’ not sure if the still say that.

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The advice I have been given is Libre is ok for dosage for food but not for corrections as CGMs are less accurate when high or low.
Add to this that Shuggah and Libre will use different algorithm to convert the ISR to BG and they are 15% accurate, these values are within tolerance.
(If the "real value is 4.0, this could be reported as anything between 3.4 and 4.6)
If you are concerned, you should take a finger prick reading.

In Response said:

The advice I have been given is Libre is ok for dosage for food but not for corrections as CGMs are less accurate when high or low.
Add to this that Shuggah and Libre will use different algorithm to convert the ISR to BG and they are 15% accurate, these values are within tolerance.
(If the "real value is 4.0, this could be reported as anything between 3.4 and 4.6)
If you are concerned, you should take a finger prick reading.

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The instruction used to be as I stated but that may have changed.. I don’t care as I use Dexcom now

Chevyjay said:

I agree when I first got the freestyle a few years ago it was always supposed to be backed up by regular blood tests, the reading on these are 10 mins behind normal levels as they are taken from the fluid not actual blood. Do I ever perform blood tests rarely now only if a reading from the sensor seems a bit off

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It’s the reason the official reader has a test strip port

Chevyjay said:

the reading on these are 10 mins behind normal levels as they are taken from the fluid not actual blood.

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Interstitial fluid is 10 minutes behind blood with regards to changes in blood sugars.
The readings reported on Libre are NOT behind.
As has been reported many times, the algorithm Libre uses to convert interstitial fluid readings to blood glucose readings takes this delay into consideration by extrapolating the current trend. Therefore, the majority of the time, the "estimated" current BG is for now. The only time this can be an issue is when teh trend changes direction in the last 10 minutes such as when correcting a hypo. This is why Libre can take longer to register a hypo recovery and may report a lower reading than a finger prick. It is why it is recommended to use a finger prick reading to measure hypo recovery.

In case you missed my point: Libre readings are for NOW they are NOT DELAYED!

In Response said:

Interstitial fluid is 10 minutes behind blood with regards to changes in blood sugars.
The readings reported on Libre are NOT behind.
As has been reported many times, the algorithm Libre uses to convert interstitial fluid readings to blood glucose readings takes this delay into consideration by extrapolating the current trend. Therefore, the majority of the time, the "estimated" current BG is for now. The only time this can be an issue is when teh trend changes direction in the last 10 minutes such as when correcting a hypo. This is why Libre can take longer to register a hypo recovery and may report a lower reading than a finger prick. It is why it is recommended to use a finger prick reading to measure hypo recovery.

In case you missed my point: Libre readings are for NOW they are NOT DELAYED!

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This is interesting, is this listed somewhere as a fact/feature. I've heard it mentioned quite a lot recently but I'm not sure where the information originally came from. When I last used the app it certainly used to lag (and there was never any talk of it predicting current glucose, simply that it reported current interstitial values), but they may well have updated their algorithms as it's been quite a while since I used it (though without knowing what and when you've eaten, I guess they can only follow the line trajectory by fitting against previous points - would be interesting to know.)

In XDrip+ when you do a fingerprick test it's moved ~8min into the future, so the whole app reports in CGM-time, which is ~8min in the past (I'd have to look at the source code to confirm the exact number.) This is quite confusing when you start using the app, and in many ways I think it would be better to have all the CGM readings moved backwards in time, and differentiate between the actual readings and the projection that XDrip+ provides which is partly based on the trajectory of a line fitted to previous data points, and partly down to modelled behaviour as it knows about IoB and CoB and their aggregate effects on blood glucose.

There is also the question of variable interstitial times (between people and activities), but that's perhaps for another day.