Libre sensor first day

Squeal of excitement.... I've had a Freestyle Libre attached to me for, oh, 9 hours now and have already scanned it a gazillion times. But the purpose of this post is to ask what people's experiences are of how the sensor performs for the first 24 hours?

I did find several posts about this earlier, but for the life of me I can't find them now. My half-memory is of a graph which started low and drifted up over the first 24 hours or so, and then became "reliable", i.e. in tune with the wearer's meter readings. So I wasn't too worried when the first scan I got told me I was 3.4. Given that I'm T2 on metformin and was feeling fine, I didn't think that was real. It was soon up in the 5's, which I was very pleased with - although it does seem to be reading about 1 mmol/l lower than my meter.

However, the numbers do seem to have been changing a bit more rapidly than I would expect. For example - these numbers around my evening meal:

Before: 5.1
30 minutes: 4.2 (***??)
60 minutes 5.9 rising
90 minutes 6.4 rising
150 minutes 5.0 level
180 minutes 4.8 level

I guess my main question is how I managed to dip 30 minutes after eating.... unless it's a compression thing.... I wear short sleeved shirts for work, and in certain positions (e.g. when I lift my arm up to scan) it's possible the sleeve is pressing on it.

Just scanned again: 4.7, and feeling hungry. I feel a snack of nuts coming on.

The meal was keto shepherds pie (cauli mash over lamb mince) with broccoli and green beans, then some strawberries and raspberries with Greek yogurt. No more than 15g total.

So you're suggesting, @phonik2K, that if I still have some first phase insulin and ate a sufficiently low carb meal, my level could indeed dip after 30 minutes, but then come up later?

@Bluetit1802, I knew that really, but I'm impatient. Do you suggest I don't pay too much attention to my first day's data, then put the next sensor on 24 hours before the current one expires?

Gotcha, thanks. I just installed the PC software, I will investigate.

BTW, do you know - when I scan, does that force it to take an extra measurement, or does it calculate based on interpolating the data it has taken? Plus I think I read somewhere that it measures every minute but only records every 15 minutes, does anyone know how that works?

I noticed the readings were out of order.... I guess the thing is to sort them by time. I wondered, though, if somehow the automatic readings were time stamped an hour out? I'm going to investigate that more closely.

I've only marked some of the things I've eaten.... cos I forgot. It will take a while to get in the habit, I'm sure. Then of course it invites you to say how many grams of carb you've had, with 15 being the default. I wonder whether it might be more helpful for me to record what I've eaten rather than guessing the carbs, because I don't want to get into measuring all my food.

So far, I conclude it is really aimed at T1's, because there's a lot of provision for recoding/calculating insulin, plus the scale goes up to 21, and you can't change that. It will be a very bad day if I ever reach 21 - I would appreciate being able to expand the scale between 4 and 10, say. I guess I can do that by exporting the data and making a graph out of it.

I am also very glad that I did buy the reader after all and not just rely on using my phone - because it is a pig to get it to scan, and the app typically stops 2 or 3 times before it actually takes a reading. That's on a Samsung S4 mini, I dare say other models might be more stable.

Oh - and I've discovered my dawn phenomenon starts somewhere before 6am and BG rose fairly steadily till something after 10, after which it came down slightly and then remained steady ish till lunch. I've also discovered that lying on the sensor gives you very low readings.... fortunately, I don't often sleep in a position which does that.

2nd day.... DP again started between 5.30 and 6am, BG rose steadily till about 10am, then fell until lunch.

I had a lunch of avo, cheese and bacon on flax seed bread (in a cafe, no less) and got no rise at all from that. That confirms to me that the lamb koftas I had yesterday had carbs in, because I spiked 3 points from those!

I think my first target is going to be the magnitude of my morning rise. I'll keep a record of the change between 5.30 and 10 am and try different (or no) evening snacks, morning drinks, ACV before bed, possibly a small breakfast, and see what happens.

I don't keep a food log, @bluetit. I'm willing to do one short term for the purposes of experimentation. I am adding the note to say when I've eaten, though - hoping that the Meal Patterns report will eventually get populated with something useful, because as yet there is nothing there.

Ooh, I'm gonna try that!

A week in and I am now a Libre expert ;-)

Anyhow, last night, this happened:

23/02/2017 05:24 0 3.7
23/02/2017 05:39 0 2.8
23/02/2017 05:54 0 2.2
23/02/2017 06:25 0 5.2
23/02/2017 06:34 1 5.3
23/02/2017 06:35 1 5.4

It would appear I went hypo (this has happened a few times now - still not sure if it's lying on the sensor or genuine), but if you look at the timestamps, a reading was missed out between the lowest point at 05:54 and the next reading at 06:25 - by which point I was back in the 5's. I then obviously woke up, cos the last two readings are me scanning. It then went down a little into the upper 4's, before beginning its DP rise.

So - looks like a Somyogi effect.... but why the missed reading? Any ideas?