A bit confused with new Freestyle Libre2

[DancingStar]

I've had my new sensor since Monday. I'm using the reader supplied by Abbot, not my phone.

There is quite a big discrepancy between what my reader and a Tee2 blood glucose test shows. I appreciate they measure different things (interstitial fluid v capillary blood) so the readings will be different. That's fine, I can live with that.

What I am finding a bit confusing is that my alarm goes off, I scan my sensor which shows 3.6, I check with a finger prick and it shows 4.8. Now, if my finger prick had shown 3.6 I would definitely be starting to feel unwell & would have been reaching for my jelly babies. 4.8 and Id feel fine (which i do), I'd just be keeping an eye on it but probably wouldn't take any action.

But, what about 3.6 measured on my sensor? Am I in the zone when I should be trying to get my blood glucose up or not? I don't want to end up going over my target - but my target measured how? With my sensor or with my finger prick? Which is most accurate? It's all so confusing.

Also, as a quick aside, my DSN said Libra readings are now acceptable to DVLA, although I'm sure I signed their form which said I had to do finger prick measurements. Can anyone enlighten me?

 

[Bruce Stephens]

But, what about 3.6 measured on my sensor? Am I in the zone when I should be trying to get my blood glucose up or not?

Up to you, really, but probably yes, you should be trying to get above 4.0 as measured on the sensor. All our measurement devices have a certain error margin so there's no one correct result.

A difference of 3.6 and 4.8 feels to me like probably close enough, and for convenience I'd be trying to stay in range according to what the sensor says. And yes, that probably means I'm a bit higher than I could be but I'm OK with that. (I seem to remember a study testing exactly that which found that following CGMs was worthwhile even though the CGMs weren't all that accurate.)

 

[Robin]

Also, as a quick aside, my DSN said Libra readings are now acceptable to DVLA, although I'm sure I signed their form which said I had to do finger prick measurements. Can anyone enlighten me?

When the Libre first came out, it wasn’t accepted for DVLA purposes, but that changed. You can now rely on a Libre reading for driving, provided that you always carry a meter and strips (or the reader and compatible strips) with you in the car at all times, and do a finger prick if your levels are low, or you feel the readings aren’t in accordance with how you are feeling at the time.

 

[rebrascora]

Generally, we take the BG reading as the one we go by because the Libre reading is kind of predicted via an algorithm.
In that situation, where I didn't feel hypo I would have just 1 jelly baby (5g carbs) to nudge my levels up a bit and keep the Libre happy 🙄 without risking pushing levels up too high..... unless I had food on board which was digesting and would bring me up anyway.... so say this reading was within an hour of having breakfast.... assuming the arrow on the Libre was horizontal. If it was sloping downwards I would have a single JB even if there was food in my system.

As regards DVLA and driving, we are allowed to use the Libre reading for driving but a finger prick takes precedence over it, from what I understand, so if in this case, you were about to drive and Libre said 3.6 but you didn't feel hypo and finger prick said 4.8 then I would say you were within the guidelines to eat a jelly baby or two and head out on your journey.

Libre generally exaggerates lows and highs, so if there is any doubt, the finger prick reading is the one to go for UNLESS it does not correspond with how you feel. ie if finger prick said 4.8 but you felt hypo then you wouldn't drive and in that situation I would probably do a second finger prick to clarify.... make sure it wasn't a rogue test strip of some contamination.

 

[DancingStar]

This is all very helpful, thank you.

 

[Bruce Stephens]

In that situation, where I didn't feel hypo I would have just 1 jelly baby (5g carbs) to nudge my levels up a bit and keep the Libre happy 🙄 without risking pushing levels up too high

Yes, that's what I'd do, too: make the alarm go away but no need to panic.