New guy from Canada

[JNB]

I recently discovered I have Type 2 diabetes, after contracting covid in December 2023 I started suffering from vision loss in February and then was diagnosed with type 2. I started reading this post due to the Libre 2 sensors I have been using since February 12th. I find that every sensor I use that would be 12 so far have quite a different reading than my one touch finger prick. I have gone on a strict diet since February. No grains, No sugars, No fruit, no High starch vegetables or any that are from the night shade group and No dairy. I have lost 45 LBS and another 20 to hit my target but my question is my Libre 2 will read 6.5 prior to eating and a finger prick will read 5 an hour or two after eating my Libre 2 will say 7.8 and a finger prick will say 6.4. in the morning my finger prick will be 4.8 and my Libre 2 will say 6.4.

I would like to know the other folks experiences with this. I know that a Libre 2 reads from the fluid around your cells and does fluctuate with eating and fasting but My doctor said he can not use it for data because it is not at all capturing data that reflects the correct number. The peaks and valleys are also very dramatic compared to the finger prick.

 

[Inka]

Welcome @JNB 🙂 You might find this thread useful:

CGM limitations and precautions

Moderator Note: This helpful reply was copied from another thread as it details some of the commonly experienced limitations of continuous glucose sensors. My blood sugar has been in perfect range for days now, but although I haven't changed anything, I'm starting to get very short periods of...

forum.diabetes.org.uk

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[s'nic]

Welcome to the forum 🙂

 

[Maz2]

Welcome to the Forum. I am sorry I have no experience of the Libre 2 but others will have and hopefully should be along to help.

I am sorry to hear about the vision loss. Is it OK now? Was it related to the diabetes?

 

[Proud to be erratic]

Welcome to the forum, @JNB.

Your Dr is right. The readings obtained from finger pricks or Libre do provide a general indication about how you are doing with your BG management day to day - but they are measuring something very different than your HbA1c which is providing a count of the average number of glycated cells over the last 3 months and giving answers in different units. You might find it helpful to have a look at this thread from the start of the Newbies section

https://forum.diabetes.org.uk/boards/threads/blood-glucose-numbers-what-do-they-mean.110434/

Libre does provide in its various reports an attempt to create a correlation between libre interstitial glucose readings and a likely future HbA1c, but the reports are not authorative enough to confirm a medical diagnosis of diabetes. That still needs rhe tried and trusted HbA1c measure.

The peaks and troughs on your graph can be very misleading. Results from 24 hours are compressed into a portrait screen size and do look much more dramatic than they really are. So, while it should be your aspiration to get a less mountainous picture from that graph you can never get anything near a taut and level "shortest distance" graph from one end of the day to the other. What any CGM like Libre can do very accurately is to document how many of all CGM readings are in Range. An International consensus has defined bottom of range is 4 and the top is 10 mmol/L here in UK and Europe. So when you read about people's Time in Range they are referring to the time they achieve staying between 4 and 10.

 

[everydayupsanddowns]

I think perhaps your Dr is being a little too dismissive of the technology if he says “it is not at all capturing data that reflects the correct number”.

There will be some differences between sensor glucose readings and capillary blood, partly because of the delay in glucose values in interstitial fluid changing, but these devices are carefully engineered to provide reliable information to help with glucose management. Including in Libre 2, sufficient accuracy to be recommended for use in calculating insulin doses.

It is interesting that Libre consistently differs to your One Touch, but that doesn’t conclusively show that one is ‘right’ and the other is ‘wrong’. All of these devices have permitted margins of error, and it could well be that for your specific blood chemistry your One Touch is reading a little lower than lab values (and Libre a little higher)

I’ve used various fingerstick meter brands over the years, and when switching between them I had to get used to their general performance based on what I was used to. Comparing meter-to-meter rarely gave the same value.

 

[Docb]

I would also add that although the various measuring devices are amazing bits of kit they do not have the precision suggested by giving readings to one decimal place. Having spent years measuring stuff in laboratories one of the things I looked at when I was given a meter was to get an idea about how useful were the numbers which popped up on the screen.

I came to the view that when it came to comparing numbers, it was best to round the reading to the nearest whole number and assume an error of +/- 1. So, your 7.8 reading is best treated as somewhere between 7 and 9. Your 6.4 reading, by the same reasoning is somewhere between 5 and 7. Since the ranges overlap, it is quite possible that readings of 7.8 and 6.4 could be obtained from the same sample. Test all 10 fingers and thumbs one after the other using the same meter (as I once did) and you will see what I mean because you will get a range of numbers.

I have never used a Libre but I am quite sure that if you slapped 10 of them on your arm they would give a range of readings, probably wider than that you get from 10 finger pricks. Thats because their sensors react to interstitial fluid rather than blood which makes the sums going on in the microprocessor much harder when it comes to deriving a "blood glucose" reading from a tiny voltage produced by some chemical reaction going on at the sensor tip.

Where does this leave you? The important thing is that introduction of measuring devices has transformed the way in which diabetes can be managed. Continuous monitoring tells you how things are changing and give warnings to the user that something requires attention. Invaluable for those with T1 diabetes. For those with T2, the finger prick is brilliant for sorting out the effect of food stuffs and if you look at readings of over time you can get an idea of how things are going generally.

They would be even better if they were more precise but I doubt they will ever be. My message to anybody getting into blood glucose monitoring is to work out what the systems are good for and exploit that. Don't try and interpret data where all you are working with is system noise. That is very frustrating.

 

[Bruce Stephens]

I have never used a Libre but I am quite sure that if you slapped 10 of them on your arm they would give a range of readings, probably wider than that you get from 10 finger pricks.

In case anyone fancies trying that (because they found a whole lot that had fallen off the back of a lorry or something), I'd be curious about the practicalities of doing it. I'm not sure I know how it could be done without 5 or 10 phones.

I know Juggluco is fine reading from two sensors at the same time but I'm not sure whether it supports more. The main use-case is to start a new sensor and compare the old and new, which I find are indeed a bit different.

 

[Docb]

That was a bit of whimsy to illustrate a point @Bruce Stephens. Mind you, I bet Abbot have done the equivalent in the lab on test solutions and I bet they will never publish the data!

Just to reinforce the point, I am not some sort of technology phobe - spent most of my life pushing technical boundaries and my name is on a few technology based patents.

My plea is for people using some technology to recognise what it can do well and to exploit it to the full. You also need to appreciate that all technology has boundaries but you normally need to work those out for your self because the sellers of it won't make any effort to educate. For example, all the meter makers know that the number after the decimal point is meaningless but you will never see that explicitly said on the packaging.

 

[Bruce Stephens]

That was a bit of whimsy to illustrate a point @Bruce Stephens. Mind you, I bet Abbot have done the equivalent in the lab on test solutions and I bet they will never publish the data!

Of course, yes. It would be crazy to do. I know that a few people have worn multiple sensors at the same time, but almost always just two or three, and for comparing different models.

The tests that manufacturers do show us are from people using the sensors as intended and show that (of course) they're not as accurate as we might hope. As you say, the decimal point of precision is in no way an indication of accuracy.