Well, this is a surprise.....

[everydayupsanddowns]

Thanks for the update @NewDawn

The rises in your glucose levels do seem fairly short-lived and the peaks were relatively modest in comparison to my efforts some days!

You might like to browse this thread which links to a fairly large 2019 study that looked into CGM responses of healthy subjects without diabetes.

It may give your results some context and background?

Thread 'BG Profiles in Healthy Non-Diabetics'

Apr 11, 2022

Continuous Glucose Monitoring Profiles in Healthy Nondiabetic Participants: A Multicenter Prospective Study

This study provides normative sensor glucose data in a healthy, nondiabetic population of children and adults.

academic.oup.com

A fairly large study from 2019 seeking to map out what "normal" BG profiles look like during the day and overnight, using CGM measures; often see it cited. Perhaps useful resource for people looking to benchmark themselves against "normal" etc.

Units are mainly in American for BG (mg/dl: divide by 18 for mmol/l) and for HbA1c (%; easy to find tools on-line for conversion to mmol/mol).

There is some circularity: the main thing for deciding whether somebody is "non-diabetic" is their HbA1c, so no surprise if BG profiles are...

• Eddy Edson
• Replies: 2
• Forum: Links

• 

 

[NewDawn]

Thank you.

I had to go into the study to work out what was going on and I found a table from which I have extracted the top. I understand that this contains average BG levels over 24 hours for non-diabetic patients split into age groups.


This suggests a mean BG level of 104 +/-9 mg/dl (5.78 +/- 0.5 mmol/mol) for those aged 60+. In the immediately lower age group the numbers are 99 +/-6 mg/dl; 5.50+/-0.3 mmol/mol.

Is that a correct interpretation? My average BG, albeit a really small sample size is 5.0 mmol/mol.

I also found this calculator on the diabetes.org.uk website which suggests to me that my estimated HbA1c based on this mean BG level is 28.4. (Again, very early days.)



Have I understood the situation correctly? (For the avoidance of doubt, I am not asking for medical advice. I have an appointment at my GP on the 14th to discuss the results.)

 

[everydayupsanddowns]

I also found this calculator on the diabetes.org.uk website which suggests to me that my estimated HbA1c based on this mean BG level is 28.4. (Again, very early days.)

Have I understood the situation correctly? (For the avoidance of doubt, I am not asking for medical advice. I have an appointment at my GP on the 14th to discuss the results.)

You can’t directly convert between fingerprick mmol/L levels and an HbA1c - it’s an estimate (guess) at best. The formulae (there are several in circulation) are ‘best fit’ from historic pairs of average fingerstick glucose and HbA1c values. Generally I find they underestimate my HbA1c by a notch or two - even from 24hr sensor average data.

The styling also looks like it might be .co.uk (the red commercial website) not .org.uk (the blue charity website)

To convert to/from mg/dl to mmol/L (note /L, not /mol!) you need to divide or multiply by 18 (which they have done in the text you posted)

104mg/dl = 5.78mmol/l for those aged 60+
and
99mg/dl; 5.5mmol/l in the lower age group.

 

[NewDawn]

This is where I have got to.

Have swapped cereal, golden syrup and a lot of protein bars for wholegrain toast, fruit, zero fat yogurt and trail mix. Below is the summary page from my CGM. I think that the sensor started to die on the 15th as the BG numbers start a significant downward trend thereafter and the FP tests are significantly higher than the CGM figure.

Average BG = 5.2 mmol/L. GMI 37 mmol/mol, estimated A1c (from the app) 30 mmol/mol. The manufacturer cannot tell me why there is such a discrepancy between the latter two numbers as they seem to have the same definition. I trust the app number as it foots with the converter I mentioned in my previous post.


The plan is to stick with what I am doing. I have managed to negotiate 3-month BG and cholesterol tests with the GP, but have bought a Thriva kit to test both in a month.

Thank you to everyone for all your valuable experience.

 

[NewDawn]

Hello, me again.

Today I had my three-monthly HbA1c test. The good news is that it is 39, down from 42. Being me, I still have some questions, however.

I have now used two Libre GCM and the results are very similar, they also foot pretty much with the FP tests. Here is the more recent GCM report



So today's HbA1c test is pretty close to the GMI indicator of 37 mmol/mol.

But my average glucose is 5.1 mmol/L. If I use the convertor in the diabetes.co.uk website, this should correspond to an HbA1c of 32 mmol/mol.

On top of that, looking at a typical day's readings from the GCM, to my ignorant eye, I seem to be able to control my BG. There is a spike after I eat, but the spike down is comparably steep to the spike up.


My questions are:

1) Why is the conversion from average BG to Hb1Ac so far apart from the actual and GMI?
2) On the basis of the graph immediately above, how well am I controlling my BG?

Thank you.

 

[Bruce Stephens]

1) Why is the conversion from average BG to Hb1Ac so far apart from the actual and GMI?

I think the sensors are reading a bit low for you.

2) On the basis of the graph immediately above, how well am I controlling my BG?

Just on the numbers reported, you're low for a surprising proportion of the time. However, I think that's probably not really happening. Maybe it is, though: people without diabetes do sometimes fall to ~3.5 in the early hours so maybe you're just doing that?

Otherwise the graph looks fine to me: very normal looking.

 

[JimmyBlue]

@NewDawn Welcome to the forum. With respect to the Libre 2, I have had two of those now and I find them useful in that they give you a view of you BG over the whole day for 14/15 days. But, it is very easy to become overly obsessive about the readings especially if you are also taking finger tests and the results don't match (the Libre is about 15 mins behind). I am currently just finger testing and miss the daily view, but at the end of the day so longer as I am under 8.5 at two hours post meal I am happy.

In terms of your diet, I went the low carb route despite being 13St 10lbs and a waist of 32 inches. I am now 12st 8lbs and possibly 30 waist. The cause, assuming current tests don't reveal any medical issues, is simply down to not upping my fat and protein amounts. By making sure I eat plenty of Greek yoghurt, snacking on nuts (love 'em) and making sure I eat more meat, things seem to be stabilising. I also find using things like the recipes for rolls on the Freshwells app really helpful as well, as they provide a lot of protein (lots of mozzarella) and fat.

 

[JITR]

1) Why is the conversion from average BG to Hb1Ac so far apart from the actual and GMI?

The three tests measure three different things: BG - glucose in a blood sample; Hb1Ac - percentage of glycated hemoglobin cells; CGM - properties of interstitial fluid.

When you look at the results of studies comparing their values for different individuals you find scatter diagrams something like this one (X/Y scales with normalised values):



I have drawn the blue line to show where everyone expects their values to be. But the red squares are all over the place because we are all different.

 

[Docb]

@JITR - Where did you get that diagram from? What are the scales and what is meant by "normalisation".

I have shown many times that my data, collected over the last few years, shows a decent correlation between Hba1c and average glucose readings over the 90 days preceding the HbA1c test. It is good enough to predict my hbA1c within a couple of units. I would love to get hold of some raw data to see if my correlation is close to any others. Hence my question.

 

[NewDawn]

Still not clear which measure, Hb1Ac or average BG, is a better determinant of the likelihood of diabetes.

 

[JITR]

@Docb
I googled "hbA1c scatter chart images" or something like that. Umpteen charts come up, including the one with the chart I chose for its visual impact and the number of patients. The units appear to be mg/dL.

From the abstract: The fasting plasma glucose levels of 3891 diabetic patient samples (1497 male, 2394 female) were obtained from the laboratory information system used for HbA1c testing by the Department of Internal Medicine at the Izmir Bozyaka Training and Research Hospital in Turkey. These samples were selected from patient samples that had hemoglobin levels between 12 and 16 g/dL. The estimated glucose levels were calculated using the following formula: 28.7 x HbA1c - 46.7. Glucose and HbA1c levels were determined using hexokinase and high performance liquid chromatography (HPLC) methods, respectively.

According to Dr Nicola Guess, who is running the NewDawn project programme, there is a a dearth of longitudinal studies, for obvious reasons I suppose (length, cost, control). Might you be able to get some comparative data from a few of the forum members who keep records systematically?

 

[NewDawn]

Now just trying to get over the coincidence of that project name: my version of "NewDawn" came from when I changed career 17 years ago.

 

[JITR]

Still not clear which measure, Hb1Ac or average BG, is a better determinant of the likelihood of diabetes.

Experts say a certain peptide test would be better. It indicatesthe condition of the beta cells in your pancreas. It's not yet ready for routine use.

I'd say people should be concerned about the likelihood of T2D and cardiovascular complications when their HbA1c is in the prediabetic range 39/42-47, especially when rising. There is close to 100% chance you can avoid diabetes at that stage by sensible changes in diet, exercise and lifestyle.

CGM data may be a viable alternative now or in future, but I have no knowledge of that.

 

[JITR]

@Docb
Might you be able to get some comparative data from a few of the forum members who keep records systematically?

@Docb.

See the following quote from this article: https://academic.oup.com/jcem/article/104/3/707/5183246

'Furthermore, when serial paired HbA1c and fructosamine measurements were performed in patients who happened to have wide variations in their control, the within-subject relationship became essentially a perfect correlation. Translation: This provided additional evidence that there was a tight physiologic relationship between the two glycemic measures that was stable over time within individuals, even if it deviated from the average population relationship. That supports the notion that the dispersion or “noise” reducing the correlation in population studies is not exclusively due to technical assay issues but rather to real biologic differences between people.'

 

[JITR]

@NewDawn
In view of the above, looks like you have everything well under control if (a) your CGM baseline glucose level is low enough and (b) your CGM peak levels are not too high and (c) you are otherwise healthy.

 

[Docb]

@Docb.

See the following quote from this article: https://academic.oup.com/jcem/article/104/3/707/5183246

'Furthermore, when serial paired HbA1c and fructosamine measurements were performed in patients who happened to have wide variations in their control, the within-subject relationship became essentially a perfect correlation. Translation: This provided additional evidence that there was a tight physiologic relationship between the two glycemic measures that was stable over time within individuals, even if it deviated from the average population relationship. That supports the notion that the dispersion or “noise” reducing the correlation in population studies is not exclusively due to technical assay issues but rather to real biologic differences between people.'

@JITR - whenever I have talked about my correlations I have always added the rider that they reflect my system and the way I collect my data and derive the averages. Anybody is welcome to the equations, but use them at your peril is my advice, you are a different person and will collect your data differently! I have asked in the past if anybody had any data sets for comparison but understandably I have had no volunteers!

One thing I have looked at is overall average in the 90 days prior a HbA1c and my waking average. I look at waking readings because they are the nearest thing to a fixed point in the scheme of things. Both give good correlations. I use both correlations to predict my current HbA1c. As of this morning, the 90 day overall average is predicting an HbA1c of 46 whereas the 90 day morning average predicts 50. The HbA1c taken a week ago was between the two at 47.

The one thing I have not done is put an error bar on the predictions -- my stats really are rusty and I would have to go back to scratch to make sure I was doing it right. I am guessing that the difference between the predictions would not be statistically different at any sensible confidence level and for me, the best interpretation is that both give a decent estimate of my current HbA1c. An estimate good enough to work with and good enough to raise warning bells if it were creeping up to levels that might concern me.

It is all good fun and I hope illustrates to members looking at their meter averages and wondering about their HbA1c, that there is a lot of fuzzyness about. My own thought is that if your overall average on your meter is less than 8 then your HbA1c is likely to be below diagnosis level.

And @Eddy Edson (as always) makes the very valid point that you can get the same average from very different distributions of the data. Don't think I could work out whether that might be significant in my data analysis so I will repeat ...my comments are on my body, my system of taking BG readings and my way of looking at the results. Works for me!

 

[CliffH]

@JITR - whenever I have talked about my correlations I have always added the rider that they reflect my system and the way I collect my data and derive the averages. Anybody is welcome to the equations, but use them at your peril is my advice, you are a different person and will collect your data differently! I have asked in the past if anybody had any data sets for comparison but understandably I have had no volunteers!

One thing I have looked at is overall average in the 90 days prior a HbA1c and my waking average. I look at waking readings because they are the nearest thing to a fixed point in the scheme of things. Both give good correlations. I use both correlations to predict my current HbA1c. As of this morning, the 90 day overall average is predicting an HbA1c of 46 whereas the 90 day morning average predicts 50. The HbA1c taken a week ago was between the two at 47.

The one thing I have not done is put an error bar on the predictions -- my stats really are rusty and I would have to go back to scratch to make sure I was doing it right. I am guessing that the difference between the predictions would not be statistically different at any sensible confidence level and for me, the best interpretation is that both give a decent estimate of my current HbA1c. An estimate good enough to work with and good enough to raise warning bells if it were creeping up to levels that might concern me.

It is all good fun and I hope illustrates to members looking at their meter averages and wondering about their HbA1c, that there is a lot of fuzzyness about. My own thought is that if your overall average on your meter is less than 8 then your HbA1c is likely to be below diagnosis level.

And @Eddy Edson (as always) makes the very valid point that you can get the same average from very different distributions of the data. Don't think I could work out whether that might be significant in my data analysis so I will repeat ...my comments are on my body, my system of taking BG readings and my way of looking at the results. Works for me!

It's may be worth reminding people that correlation doesn't necessarily imply causality. Also, something that's statistically significant may not be clinically significant - and vice versa.

 

[JITR]

@Docb

Robert M Cohen, who has studied the HbA1c and BG levels over the years, supports what you say. That's what I took 'a tight physiologic relationship between the two glycemic measures that was stable over time within individuals' to mean.

 

[Docb]

@Docb

Robert M Cohen, who has studied the HbA1c and BG levels over the years, supports what you say. That's what I took 'a tight physiologic relationship between the two glycemic measures that was stable over time within individuals' to mean.

I guess that is one way of putting it!