Freestyle 2, Dexcom G6 & Finger prick

[Flower3333]

This morning I started my trial on the Dexcom G6 and I’m also so wearing my Freestyle 2. I know you shouldn’t make comparisons between different machines but I thought the results for the different sensors and a blood test was interesting:

Freestyle 2 - 13.8
Dexcom G6 - 7.7
Finger prick - 13.2

 

[helli]

A couple of thoughts
- CGM are typically much less accurate above 8 or 9 (and below 4). So with a finger prick reading in the teens, I would not expect much from either Libre or Dexcom
- How long ago did you insert your sensors? My body needs a day or two to get used to the alien object I have just inserted. As a result, if I activate the sensor on the day I insert them, the first day's readings are entirely unreliable.
- Have you calibrated the Dexcom?

I have used LIbre 1, Libre 2, Dexcom G4 (a long long long time ago) and Decom G6.
In my experience, Libre 2 seems to be the most accurate at high numbers, Dexcom G6 is most accurate for "normal numbers", Libre 1 was inaccurate with the official app but usable with xDrip which I could use to calibrate and the G4 was frustratingly inaccurate.

 

[Pumper_Sue]

I have always found that the first 24/48hrs are a waste of time with the G6 as so inaccurate and I would never ever not test before a meal or correction bolus.

 

[DavidG89]

I find the free style 1 and 2 to be very inaccurate. My experience is that it shows significant higher reading's when you are a bit high say for example 10 mmol on a blood finger prick test has show results as high as 15 or 16 and climbing, 30 mins later on a finger prick I am down to 8mmol and the libre shows a steady 15mmol. I have had sensors replaced and had put it down to a faulty sensor, however this is a regular thing for me, then when I check and it shows I am low with th arrow pointing downbfor example 3.5mmol, I do a finger prick test and shows I am sitting comfortably at 5mmol. I find it is only accurate between the ranges of about 5-9mmol. I use it as guidance and handiness but I would always double check with finger prick test.

 

[everydayupsanddowns]

Some times it can take 24 hours for a sensor to settle. Personally G6s have always tracked really really well for me. I’ve only had one dodgy one in all the ones i have used, and yes... you are right... it was one where I was checking against Libre2 for my own amusement.

I also had one dodgy Libre2 sensors, but the others have tracked really well.

And of course the interstitial ‘lag’ means there will often be a frustrating gap between capillary glucose and sensor glucose - especially when BG is bouncing around a bit (which is most of the time!)

 

[Sally71]

When we got our first Dexcom last summer we still had 10 days to go on the last Libre (didn’t want to have a gap with no sensor at all!) so that was an interesting comparison (Libre actually outlived the Dexcom by a few hours lol...). First check only a few mins after the Dexcom had started working showed Libre closer to finger prick so daughter instantly calibrated the Dexcom, and then promptly crashed through the floor the next time she ate something because Dexcom thought she was higher than she was and the pump overcorrected! Oops...
So she managed to recalibrate the Dexcom back to where it was and have found it very accurate, all the time we were comparing the two i think Dexcom was more accurate after the first one. DSN said we shouldn’t ever need to calibrate Dexcom, and having read the instructions properly now you are advised never to calibrate it within the first 24 hours because of the issue of the sensors taking time to bed in. We find most of them work pretty accurately straight away, some take a few hours, daughter prefers to change them just before she goes to bed which I don’t think is ideal, occasionally we get one which is reading low all night but then settles in the morning. Had that with Libre as well actually. Never had Libre 2 so can’t comment on that!

These days on the rare occasion we do do a finger prick to check the sensor, it’s almost always within 0.2 so rarely bother to do finger pricks at all any more, unless we are in between sensors!

 

[everydayupsanddowns]

These days on the rare occasion we do do a finger prick to check the sensor, it’s almost always within 0.2 so rarely bother to do finger pricks at all any more, unless we are in between sensors!

That’s been my experience too when BGs are just mooching along. My strip use has cut right down!

 

[pm133]

I must admit that with the Libre, I don't see any unusual pattern changes in my readings when I start a new device but I'm only a few months in so maybe I've yet to experience that. I must admit that I don't finger prick test at all now unless I go low, feel rubbish or very occasionally indeed when I attempt a bolus correction. Quite happy to trust the Libre before meals but obviously others have different experiences to me.

 

[Sally71]

When we had the Libre we also had the Combo pump, and the only way to get your BG into that to enable it to do corrections properly was by finger pricking with the Combo meter. So we had to do finger pricks 3 times a day anyway, which served as a useful check that the sensor was working. Now we have Tandem pump which links directly with Dexcom and always knows what your BG is, we don't have to finger prick any more. You can overrule the BG value, but we've found we don't need to.