Differing results

[Nanalinboy]

Hello there , I’m a newbie on this site , but looks like you may be what we’ve been looking for . We are both diabetic , and recently my partner has noticed that his level can be so different from one finger to another , this morning he checked the same finger twice , one on each side of finger , one side was 8.9 the other side was 9.2 . Does this seem normal ,has anyone else noticed this please

 

[Docb]

Hi @Nanalinboy, and welcome to the forum. What you are seeing is quite normal. A little while ago I tested all eight fingers and both thumbs just to see what the variability was. Showed me that the best thing is to round the result up to the nearest whole number and don't be surprised if the variation is +/- 1 of the average. Since that time I have never quoted a single result without rounding.

So, for me, your 8.9 and 9.2 are the effectively same and best reported as 9's. If you had banged away at all your fingers you might well have got some 8's and 10's and maybe even the odd 7 or 11. This does not mean your results are useless, far from it. You just have to take a little care in interpreting them.

A range of 8-10 on waking is a bit higher than most would normally look for and are consistent with you getting a diabetes diagnosis. Do you know what your HbA1c was on diagnosis and are you on medication or taking steps to bring your blood glucose levels down?

 

[Nanalinboy]

Hi , docb , it’s my other half , not me , but he was 23.3 when diagnosed , a friend at work tested him and almost marched him to the doctors , he’s currently around 6-7.5 on waking , but the nurse has said if he keeps his levels steady he may be able to come off his daily injection (liraglutide) and go onto ozempic one a week . Since that time he has been refusing anything even vaguely bad for you , no pies or anything like , and his bs has gone up! Today porridge for brekky , nothing else and he went from 8.9 on waking to 6.3 , thing is , he is almost eating nothing now to try and get on this new injection. Thanks for replying

 

[Leadinglights]

It should be perfectly possible to keep levels stable and even reduce them by following a sensible dietary regime. No need to completely cut carbs completely but keep them within the amount the body can tolerate. Porridge is something many people have problems with in pushing up their blood glucose level too much.
Breakfast is tricky but many people find the best is low carb having Greek yoghurt with berries and maybe a very small portion of a low sugar cereal or eggs in any form.
This link might help you find some ideas for a way forward on modifying your diets. https://lowcarbfreshwell.co.uk/

 

[IrvineHimself]

..... this morning he checked the same finger twice , one on each side of finger , one side was 8.9 the other side was 9.2 .....

In science and engineering, when making precision measurements they talk about Calibration. The subject is very esoteric, but, in this case, very relevant. Additionaly, although the [separate] Wikipedia page on Calibration Curves only deals with analytical chemistry, calibration curves are used with a wide variety of instrumentation to improve the accuracy of the measurement.

What does this mean?
I recently bought a set of electronic scales, Say I had some very accurate test weights: I could gradually add weights to the scales and note down the results. Then, gradually remove weights while again noting down the result. This would give me a calibration table for the instrument and it might look something like this:

Test Weight (oz)​	% Error: weight increasing​	% Error: weight decreasing​
0​	0​	0​
1​	-10​	7​
2​	-9​	-13​
3​	-1​	0​
4​	7​	-5​
5​	11​	-8​
6​	-14​	3​
7​	-9​	9​
8​	14​	-6​
9​	3​	-1​
10​	8​	-4​

Full disclosure: A skilled statistician, physicist or engineering will tell you that particular curve is garbage. The reason is because, rather than calibrating a real instrument, I used a random number generator to get the errors. However, it does nicely illustrate the principle.

The things to note are:

• Different test weights have different errors
• The error is different depending on whether you are adding or removing weights

As I say, the art of calibration is very esoteric and involves maths that will set your eyes rolling. With regard to a consumer level BG meter, I believe they have quoted accuracy of about 15%, but as I hope you can see from my little demonstration that quoted figure does not really tell the whole story

Edited table because I stupidly copied the error of zero as 6%

 

[Docb]

@Nanalinboy, there is something you said in your post which needs a bit of thinking about and that is the idea of things to eat that are "bad for you". When looking at food stuffs from a diabetic point of view, the big thing to think about is the amount of carbohydrate in it because it is the carbohydrate which is turned into blood glucose. Much more important than worrying about the "harmful" things you read about in the press. You will find many (if not most) on here who control their diabetes by eating a reduced carb diet and that does not mean we are frightened of eating anything. Trouble with carbohydrates is that there are a lot of different ones and different people react differently to them. So the porridge brekkie will contain a lot of carbohydrate. Some can cope with it some cannot.

Since you are testing I would suggest you get yourselves a note book and do some structured tests around meals. Test before eating and test a couple of hours afterwards for a few meals and then look for patterns. What you are looking for are food types that consistently give a bigger rise in blood glucose than others. You can then begin to eliminate those things. For example, when I did it soon after diagnosis, I found that anything with wheat flour in it was a particular problem yet oats were not. All you can do is experiment and find out.

@IrvineHimself - biggest problem is sampling error in my view. The idea that each tiny drop of blood is going to have the same glucose level is a bit much for me.

 

[IrvineHimself]

biggest problem is sampling error in my view. The idea that each tiny drop of blood is going to have the same glucose level is a bit much for me.

Agreed, that is one of the reasons why the maths will make your eyes water. Having said that, in practice, you will most likely need the calibration, (or systematic) error when estimating the sampling error and variance of the sample. However, it is over thirty years since I did any of this, so I am most definitely not an authority.

As I pointed out, if you know about the subject, there is a lot wrong with my little demo. However, I think it nicely illustrates a fundamental principle of mensuration, and why you should only interpret the results within the known limits of accuracy.

As a side note: For those struggling to follow, the basic idea behind all this is what allowed scientists at the LHC to detect the Higgs Boson, and is now underpinning the hunt for a fifth fundamental force of nature

 

[leonS]

If you were to test your BG 1000 times and plotted the number of times each different result appeared, the plot would form a bell shaped curve known as a normal distribution.

Don't try this at home - it WILL make your eyes water.