Not for newbies. Boffins allowed :-) Comparable finger prick & blood test readings- type 2,

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Jenny105

Jenny105

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The correlation between these 2 readings - blood test over 3m & fingerprick, now (bottom number) isnt accurate in chart form. Ive read this on here. (my avr of 8.7 fingerprick gave 44 ITCC 3m blood test)
It would be helpful for my situation if anyone knows if there is one accurate correlation ..... Or if thats not possible.
Without going into detail my DN wants me to reach a ITCC 50 (thats the full blood test result ) I'd like to know how my average fingerprick readings relate to this. Maybe ? i can work out if my change in the number of carbs consumed is going in the right from that info . :confused: 🙂
1664217579957.jpg
 
Jenny105 said:
Or if thats not possible.
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As I understand it it's just not possible. The measures are of different things. An average probably would be closer if you have measurements across the 24 hours, but for obvious reasons we don't generally have those (well, CGMs give them, but with measurements over the whole day time in range is likely more useful anyway).

Not sure why your DSN wants you to have a higher HbA1c. Your medications don't have a risk of hypos (which is the usual reason for worrying about low HbA1c). Just about the weight loss? If so, might be worth trying to track calories and see if you're eating enough energy wise, and (presuming you are) trying to find if there's something else causing the weight loss.
 
Usually, diabetic nurses are wanting people to be in the normal range below 42mmol/mol not actually still at a level that would be still diabetic. People diagnosed at that level would be striving to reduce it.
There seems no logic to her suggestion.
 
Leadinglights said:
There seems no logic to her suggestion.
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I presume it's about the weight loss? (It also wouldn't surprise me much if the desirable HbA1c target was higher for older people, though I presume a DSN would still be fine with a lower value than the target.)
 
In principle it should be possible to get some sort of correlation between Hba1c and finger prick results because both depend on the level of glucose in the blood. It is not straightforward though, and as you observe @Jenny105 , not as straightforward as the chart suggests.

I actually have a correlation for me, and here it is.
1664222459054.png

It did actually work because the circled point, the last test I had, fell exactly on the line predicted from eight previous tests.

There are a couple of important points about this data, the most important is that I did a lot of random finger prick testing at odd times of the day in order to get as good an average as I could. I also kept lots of other things under as reasonable control as was possible. The second point is that it was me, my biological system and my method of measurement neither of which I would wish on anybody else! You can read all about it in this thread.



In reality the numbers, including those on the chart you reproduce should be though of as giving reasonable guidance rather than firm predictions. So if your finger pricks rarely get much above 8, you can expect an HbA1c around the 40's but if you never see anything below 10, then you can expect an HbA1c heading for three figures.
 
Bruce Stephens said:
As I understand it it's just not possible. The measures are of different things. An average probably would be closer if you have measurements across the 24 hours, but for obvious reasons we don't generally have those (well, CGMs give them, but with measurements over the whole day time in range is likely more useful anyway).

Not sure why your DSN wants you to have a higher HbA1c. Your medications don't have a risk of hypos (which is the usual reason for worrying about low HbA1c). Just about the weight loss? If so, might be worth trying to track calories and see if you're eating enough energy wise, and (presuming you are) trying to find if there's something else causing the weight loss.
Click to expand...
Yes the 55 is unusual Im going with it. We have an exceptionally good GP practice. Plus shortly I'll have a battery of general healt tests for completely diffferent reasons . Theres usually a phone call from the doc after these so I can ask about the 55. Its probably an interim measure.
Re weight . I ve taken a medication for 25yrs which is reknown for weight GAIN. I gained 3 stone. In the past 10 yrs the meds have been reduced 3 times. The last reduction coincided with the massive weight drop. 2 stone (I had managed to already drop 1 stone over the past 6 yrs) So my weight is only a little below what it was 25yrs ago in midlife.....Might explain that issue
 
Yes unfortunately there is no possible mathematical conversion, even if your average glucose values are coming from a continuois sensor measuring 24/7.

Blood glucose values are connected to HbA1c, but not in a matnematical way.

The conversions and formulae are generally empirical. That is they are derived as a ‘best fit’ to pairs of known data (HbA1c values and the average glucose of the person at the time). With a bunch of samples you can work out a mathematical conversion that more or less fits the sample set you have, and if there are a reasonable number of pairs of data points and people involved you can get a reasonable estimate. But it won’t necessarily work for any one individual.

Are you having lots of hypos @Jenny105 ? Or are you finding diabetes management burdensome or too intensive at the moment?

Just wondering what reason has the nurse given for wanting your HbA1c to be higher than it is?
 
Docb said:
In principle it should be possible to get some sort of correlation between Hba1c and finger prick results because both depend on the level of glucose in the blood. It is not straightforward though, and as you observe @Jenny105 , not as straightforward as the chart suggests.

I actually have a correlation for me, and here it is.
View attachment 22279

It did actually work because the circled point, the last test I had, fell exactly on the line predicted from eight previous tests.

There are a couple of important points about this data, the most important is that I did a lot of random finger prick testing at odd times of the day in order to get as good an average as I could. I also kept lots of other things under as reasonable control as was possible. The second point is that it was me, my biological system and my method of measurement neither of which I would wish on anybody else! You can read all about it in this thread.



In reality the numbers, including those on the chart you reproduce should be though of as giving reasonable guidance rather than firm predictions. So if your finger pricks rarely get much above 8, you can expect an HbA1c around the 40's but if you never see anything below 10, then you can expect an HbA1c heading for three figures.
Click to expand...
Very interesting . I can see lots of fingerprick tests are useful for this. When my result came out at 38 my avr according to the tool was around 8+. I'd been asked to do 1 or 2 tests a day at varied times over a week. The next was 44 with avr of around 9 +. I supposed Im curious because DN wanted me to be less stringent on my diet.. This chat is no good for newbies this is technical interest
 
everydayupsanddowns said:
Yes unfortunately there is no possible mathematical conversion, even if your average glucose values are coming from a continuois sensor measuring 24/7.

Blood glucose values are connected to HbA1c, but not in a matnematical way.

The conversions and formulae are generally empirical. That is they are derived as a ‘best fit’ to pairs of known data (HbA1c values and the average glucose of the person at the time). With a bunch of samples you can work out a mathematical conversion that more or less fits the sample set you have, and if there are a reasonable number of pairs of data points and people involved you can get a reasonable estimate. But it won’t necessarily work for any one individual.

Are you having lots of hypos @Jenny105 ? Or are you finding diabetes management burdensome or too intensive at the moment?

Just wondering what reason has the nurse given for wanting your HbA1c to be higher than it is?
Click to expand...
No hypos and generally managing ok . My DN thought i was being too strict on my diet and needed to relax a bit sometimes. Weve been away , carb input rose , avr rose to 10. Just curious about where this is leading. As mentioned I have some general tests coming up so I'll ask my GP about this. Now home the diet can revert to less carbs. All is ok no real problem. Thanks for asking see note about weight below
 
Well if in order to get to an HbA1c of 55 you need your average glucose to be 10ish, that doesn’t make sense to me.

The guidance for T2 BG levels always used to be

4-7 before meals and
8.5 or lower by 2hrs after meals.

Perhaps you are a ‘low glycator’ and produce lower A1c values than the average BG might suggest? Do you have anaemia at all?
 
2 tests a day really isn't going to give you any sort of "average" which is useful for this conversion graph. Those are just 2 moments in time compared to all the other seconds, minutes and hours in each 24 when you don't test. Levels may well dip during the night which is perfectly natural and then come back up in the morning so assuming you don't set an alarm and test at 2am occasionally you may be missing a lot of lower readings then.
How random is your daytime testing? Do you do one pre-meal and another post-meal every day and do you alternate the time of day or meal when you do that?
 
When I'd had a Hba1c of 42 for several years I thought I'd lower it into the 30s by reducing my carb limit from 50 down to 40 gm a day maximum. Stuck to it religiously.
So a year later I was hopeful.
Hba1c 42.
Sigh.
 
Hi thanks for everyones input. I'm about to have some tests with GP so I will get a call from her when results are in. Ive just remembered that my Metformin ran out 10 days ago .(There was an easy error that i made) My GP rushed me a new prescription but I was without Metformin for 2-3 days plus I went away for a few days after that and couldnt stick rigidly to my usual foods.
I'll get tmy readings back into line and also chat to the doc. My GP practice is excellent so maybe there is a reason behind their advice. Im in good health , active etc. The blood tests i have are pretty thorough and numerous. We shall see what comes up..... bye for now
 
Jenny105 said:
My GP rushed me a new prescription but I was without Metformin for 2-3 days
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I don't think that's much of a problem. I think it's one of those drugs whose effects stick around, so the levels might have dropped a bit but not too much.
 
PS I upped my carbs 3m ago to approx 100 to 120 a day. Prior to that they were 80 - 100 with 38 Ab1Hc in 2021 then 44 2022
 
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