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Libre 2 sensor and testing

L

Luke2

Active Member
Messages
25
Type of diabetes
Type 1
Treatment type
Insulin
Hi all,

I got a libre 2 sensor fitted about three weeks ago now. I was only diagnosed four weeks ago. Thankfully, the diabetic team were quick to act and have been fantastic.

My questions are:

I find that it’s usually 1 mmol out, does anyone else find this?

Also, how often would you finger prick during the day as well? Some days I’ve not bothered as the levels seem really good (plus, I feel good!)

Finally, how often do you check ketones? Mine were very high on diagnosis, touching 3. The last three weeks when checking it’s always around 0.2/0.3.

Thanks in advance, it’s one HUGE learning curve!
 
(Type Two) I find that I need to get to know each sensor, as some will give higher results and some lower results than my meter. I had one recently that was very excitable - if it saw a rise it would predict too high, and similarly with lows, it would go shooting down and give readings that were much lower than my meter. They generally give accurate readings when your levels are stable.
If I was type 1, I would probably be doing quite a few finger pricks each day as the libre isn't always reliable enough. Let's hope that technology will improve over time.
 
Luke2 said:
I find that it’s usually 1 mmol out, does anyone else find this?
Click to expand...
Both LIbre and finger pricks conform to a standard which allows +/-15% accuracy. So depending upon your levels, the difference between the two may vary. For example, if your "real" BG was 10, your two meters could independently report anything between 8.5 and 11.5. Therefore, a usual" difference of 1 is within this tolerance.
However, there are a few other things to consider
- insertion trauma - some people find that their body takes 24 to 48 hours to adjust to an alien object inserted in their arm. During this period, the readings may app[ear random. If you experience this, it is common to apply your new sensor a day before starting it. In your other arm, obviously.
- compression low - if you apply pressure to a sensor, it will block of the flow of fluid to the sensor. As a result, you may receive a false low. This is most common at night when you may lie on your arm with your sensor.
- interstitial fluid delay affect - CGMs like Libre do not read blood glucose. They read interstitial fluid and use an algorithm to convert this to a BG reading. A change in BG will be reflected in the interstitial fluid reading after about 10 minutes. The algorithm used will take this into consideration by extrapolating the current trend. This is great most of the time. However, if your BG trend has changed in the last 10 minutes, the extrapolation will be incorrect. This is most commonly observed when recovering from a treated hypo - your Libre will suggest it takes longer to recover.
- highs and lows - CGMs like Libre are designed to be most accurate at "normal" levels which is typically between about 4 and 9. Outside of this range, they may have a tendency to exaggerate highs and lows. Therefore, it is recommended to check a high or low with a finger prick before correcting. If you are experiencing an obvious hypo, there is no need to double check.
- factory calibration - cheaper CGMs likes Libre and Dexcom One are factory calibrated with no option for home calibration against your finger pricks. This is fine for most people but some of us find that we are slightly different to "factory man". There are unofficial apps like xDrip+ on Android and Shuggah on iPhone which allow calibration (and other features). The possible downside is that these do not upload your readings to LibreView for your DSN to review.
- faulty sensors - unfortunately, some sensors are faulty. This may be extreme inaccuracy, stopping early, disconnecting regularly, ... Abbott are very good at replacing these if you report them. I have found the online form (available on the Freestyle Libre website) very good for this. I recently received a replacement within less than a week.

Luke2 said:
Also, how often would you finger prick during the day as well? Some days I’ve not bothered as the levels seem really good (plus, I feel good!)
Click to expand...
It depends. Given the "limitations" above the advice is usually to finger prick if the reading does not reflect how you feel or if high or low.
I tend to check once a day when my levels are in range and reasonably stable. This gives me peace of mind that the sensor has not gone astray.

Luke2 said:
how often do you check ketones? Mine were very high on diagnosis, touching 3. The last three weeks when checking it’s always around 0.2/0.3.
Click to expand...
Very very rarely - only when my BG is above 15.

Luke2 said:
it’s one HUGE learning curve!
Click to expand...
Absolutely and you are doing great asking brilliant questions so that diabetes does not take over your life.
If you have a certain type of mind, the learning curve can never stop as new technology and treatments are constantly coming available.
 
I rarely test. Libre is relatively accurate for me and I trust it. I would test in the middle of the night if high alarm goes off. I then can inject the correct amount. In December I was ill and ketone testing was invaluable. However, they are expensive and my Gp would have something to say if I used them regularly. In general I perhaps use 10 a year.
It’s all about knowing how you feel and that comes with experience.
 
Luke2 said:
I find that it’s usually 1 mmol out, does anyone else find this?
Click to expand...
For me, Libre reads pretty consistently lower than blood by about 1-2 mmol/l.
I use the unofficial app DiaBox (only on Android, not in the play store) next to the official app. DiaBox can be calibrated, and has more useful alarms to my thinking. Still not perfect though!
Luke2 said:
Also, how often would you finger prick during the day as well? Some days I’ve not bothered as the levels seem really good (plus, I feel good!)
Click to expand...
Depends.
New sensor? Often, say 3 to 5 times because I don't trust it and need to calibrate.
Proven sensor? I occasionally have a day without fingerpricking but on most days I test 1 or 2 times.

I test more often around exercising because my BG can change quicker than my Libre notices, but less often than when I started exercising, I have developed a bit of a feeling on what to expect.

I always test after a hypo. I think the back of my arm is very low on my body's list of priority when it comes to where to send the glucose first. It can take close to 30 minutes after getting a >4 fingerprick for my Libre to notice the problem has been long solved.

I test multiple times after swimming (or dipping) outside, which I do at least twice a week. The water temperature has gone back up to a balmy 7.8 °C as of today, but the Libre stops working below 10 °C (gives a 'sensor is too cold' error message until it's warmed up again). And those cold swims have some spectacular effects on my numbers. On top of that, either the cold makes it confused for at least 40 minutes after, or the cold does interesting things to the amount of glucose in the back of my arm. Either way, sensor BG doesn't add up with a fingerprick at all during this time, and I choose to trust fingerprick more. Would be interesting to know what venous blood does around swimming, might be completely different yet, but no way to find out.

Mind, none of the things I do come anywhere close to what is official advice, but you asked what we do, and from your posts it looks like you want to know everything and dive head first into this diabetes thing, so here you go.
Luke2 said:
Finally, how often do you check ketones? Mine were very high on diagnosis, touching 3. The last three weeks when checking it’s always around 0.2/0.3.
Click to expand...
I've never tested for ketones in the 7 years I've had diabetes.
There are only two scenarios in which I would want to test: High BG well into the teens that won't drop, and illness with symptoms that may be caused by DKA.
Neither have happened so far, and if they do I'll curse myself for not having a means to test for ketones.
Luke2 said:
Thanks in advance, it’s one HUGE learning curve!
Click to expand...
Looks like you've hit the ground running, keep doing what you do but make sure you don't burn yourself out.
As long as it feels right, by all means, keep learning as much as you can!
But if it leads to feeling like it's all too much, by all means give yourself a break, don't expect to be perfect from the start, and allow yourself to slow down.
This is a marathon, not a sprint.
 
Wow, incredible responses. So so glad I’ve joined this forum.

My libre tends to be about 1 higher than my finger prick testing, apart from when I’m low. At this point I’m pricking my fingers like a mad man haha.

When I change the sensor, I think I’ll do a few more finger pricks those days!

Interesting about the pressure on the sensor at night as well, I’ve had a couple of times where the alarm has gone off ‘levels going low’. I do tend to sleep on my arms and I haven’t felt a hypo. In these situations I’ll definitely be finger prick testing (which I have been doing in a hypo situation).

I’ve been testing about once a day for ketones, I think I’ll stop this now as it’s always within a normal range. I’ll save them for if I go really high! Additionally, I feel absolutely incredible in comparison to five weeks ago (pre diagnosis). A lot more energy, less mood swings, extreme hunger and thirst has subsided as well.

I’m so glad I went to the doctors when I did. Sometimes, I wish I’d gone earlier, but you can’t live in regret.

So much to learn, and this forum is a fountain of knowledge.

Thank you
 
I find Libre 'variable' during its 2 week cycle

First few days you get 'insertion trauma' - readings are skewed as your body has to get used to the sensor under the skin (offset this by inserting a day before starting it)

Secondly I use software that lets me add calibrations to the readings, so if its always high or low from BGs - you can adjust the figures to match the real ones. (I use xDrip but there are alternatives)

Thirdly remember a Libre is at lease 20 mins behind a blood test, if your rising or falling it takes time for it to register.

Glad you're enjoying it - I've been using them a long time as I wanted BG on my watch with alarms on lows at night. They got me started down the path of a Fully-closed-loop (automated DIY pancreas) which is amazing, a long path but worth the effort, I now drink orange juice as a food rather than a hypo treatment My loop just handles it without fuss
 
CheeseSeaker said:
Thirdly remember a Libre is at lease 20 mins behind a blood test, if your rising or falling it takes time for it to register.
Click to expand...
As I mentioned above the Libre algorithm adjusts to take this delay into consideration.
If you use LIbreLink, this is only an issue if your trend changes during the last 15 minutes,.
I do not know whether the xDrip+ algorithm does the same thing ... maybe not.
 
Thank you for this.

How did you get it on your watch? I have an Apple Watch and I’ve had to download three different apps to get it on my watch? Yet there is a significant delay for the readings to show up on my watch. You’d think libre would design their own Apple Watch app?

Thanks!
 
In Response said:
I do not know whether the xDrip+ algorithm does the same thing ... maybe not.
Click to expand...
It does yes - predictions in any algorithm are predictions, they don't cater the spontaneity of most peoples lives (nothing can)
 
I use Android (personally find it more flexible for apps and hardware support for the odd things I do and have connected to my phone) - there are generally ways to get things working on both platforms, interesting to know you have delays between app and watch - can't help with Apple I'm afraid

I guess that Abbott don't want to get into the watch development game - support and overheads of app deployment might not give them a cost benefit - not sure how many people as a % would want a watch app, so maybe they leave it to others to provide for a section of the market.
 
I think everyone with diabetes and a libre would want it on their apple watch!
I followed these steps to get the values on my watch:
Its a shame abbott does not bother to make an apple watch app..they also did not make a reader for the libre 3..cant be that hard to make the watch app…i bet it would also boost apple watch sales.
 
I followed that as well. I do find that it is a bit delayed.

I agree, surely there would be 1000s of people who would want the app on their watch. It’s great to be able to have a quick glance at the reading, without having to constantly get my phone out.
 
TimLibre said:
I think everyone with diabetes and a libre would want it on their apple watch!
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Nope. Not everyone with a Libre is an Apple fan, feel the need to wear a chunky watch or even use a phone.
It’s great technology allow each of us to use what we want/need. Our needs differ greatly.
 
Great advice has already been given so not sure I can add anything.

I do find the libre sensors are reasonably accurate but each new one tends to have its own personality. I still fingerprick at least 4 times a day… a habit i developed and never really shook after only getting my first libre a year after diagnosis. I am only a couple years into the marathon myself.

As to Ketone testing I still have the first box i purchased after leaving hospital when diagnosed.They have expired but i still hope they are accurate enough. Not sure if different in UK but they subsidise glucose strips here in AUS but not Ketone strips…. Pretty silly if you ask me. I only test if very unwell or BGLs above 15 for an extended time … very rare for me.
 
In Response said:
Nope. Not everyone with a Libre is an Apple fan, feel the need to wear a chunky watch or even use a phone.
It’s great technology allow each of us to use what we want/need. Our needs differ greatly.
Click to expand...
They could also make it for an android watch i wouldnt care. Not going into apple/android discussions here. But when i started using libre 3 ‘normal’ readers were not even available and abbot primarily focussed on its app.

Benefits of a watch app would be to be able to monitor your bg way better.

But also for example when playing football, jogging, or any other kind of sports it is not so convenient to have your phone with you in your pocket. While sports are precisely the moments most people would want to monitor their bg a bit.

Thirdly an alarm on apple watch is far more discrete than the libre app alarms on your phone, which alerts/wakes up not only you but the full room of people you’re in.

But going back on topic, i hardly do any finger pricks anymore. When i started to use the libre 1 system, for the first weeks i would check still every day. But after a while i didnt bother anymore as the libre readers were good enough for me. Today, only at moments were the libre sensors are obviously acting strange, or if I feel differently then the value indicated, i do a finger prick, but thats rarely. For example on holiday after having a swim in the sea, they sometimes act strangely.

So even if i dont finger prick a lot, i make sure i have the possibility to do so.

Having said that, i saw some people complaing about the Libre 2’s accuracy a while ago, (and dont know if those problems are fixed now). So maybe its good to double monitor for a while if you just start using the system. Im using libre 3 now for some years and its totally accurate in most cases.
 
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