Was wondering....

[indio02]

On doing a waking up finger prick I was at 5.8. No breakfast. Did a pre-lunch prick at 1:45 and got a 5.2. Two hours after a fairly carby lunch (2 slices of sourdough toast , 2 poached eggs & whole avocado. Nuts and greek yoghurt) my result was 7.8. I will have a bowl of butternut squash soup for supper no bread.
I'm wondering how this translates into an hba1c ie for the vast majority of the day (20+ hrs) it's in normal range but for say 4 hours it's above. Is that going to negatively impact hba1c?
Thanks

 

[pjgtech]

Hi, my basic understanding is that there is no direct correlation to one, or even a few, finger prick BG tests and the HbA1c blood test.
The three monthly HbA1c is testing your three monthly average, NB: blood cells last about three months, hence the three monthly interval.
Whereas the finger prick BG test is just doing a one off, spot test.
If you have many finger prick test results over a long period, say several weeks, then that would give an indication of where your BG levels are, (on average over that time).
There are a couple of conversion charts, see attached, but as above they are just "guides" and not not 100% accurate.
Plus, also bear in mind that there are many things that can affect you BG levels, (eg: being tired, stress, an illness, what you eat, if you exercise, etc) and your BG levels will fluctuate up and down throughout a typical day.
Cheers

 

[JimmyBlue]

Hi @indio02 I'm not sure that you can do that kind of assessment, although if I am wrong I am sure someone will correct me. The finger prick test is simply a point in time check and your BG can move around a lot between tests. The HbA1c test looks at the average amount of excess BG picked up by red blood cells over a two to three month period. Therefore the measure are slightly different.

If you use a sensor like the Libre2, that does give you a HbA1c forecast based on the continuous monitoring it does but I have to be honest that forecast is often no where near the actual result of the HbA1c test (as I recently found out). It may be different if you wear the sensor(s) permanently over a three month period.

 

[indio02]

Thanks both... my fault completely I've not explained my question very clearly. I'm trying to understand how an hba1c number is arrived at in terms of eating.
If your Hba1c is 50. You then spend 1 month eating nothing but carbs bread, pasta potatoes etc. You then spend 2 months eating virtually no carbs at all. When you re-test at month 3 what will affect your hba1c more.... the 1 month of carb overload OR the 2 months of virtually no carbs? Does 6 days a week of no carbs mitigate 1 day a week of lots of carbs over a 3 month period.
I'm trying to understand what pattern of eating elevates an Hba1c result as I'm assuming its not just one meal/day of excess carbs.

 

[Lucyr]

I'm trying to understand how an hba1c number is arrived at in terms of eating.

It isn’t. You can’t estimate your hba1c based on your eating.

 

[indio02]

But if you eat lots of carbs your Hba1c will be higher than if you restricted them.

 

[Lucyr]

But if you eat lots of carbs your Hba1c will be higher than if you restricted them.

Not necessarily. It depends on whether your body makes more insulin to cover them, or your medication or exercise helps you to cover them

 

[Leadinglights]

But if you eat lots of carbs your Hba1c will be higher than if you restricted them.

If you eat more carbs than your metabolism can cope with so there is excess glucose in your system then it sticks to your red blood cells and will stay there for the life of that cell which on average is about 3 months. The more frequently that happens then the higher your HbA1C will be as more of those red blood cells will have glucose attached, once attached even low carb will not detach it but less cells will have glucose attached. This is a very simplistic explanation as I interpret it.
The guide is that if finger prick readings are consistently 4-7 mmol/l fasting/morning and before meals and no more than 8mmol/l 2 hours after eating for the 3 months prior to the HbA1C test then the more likely it will be in normal range.

 

[everydayupsanddowns]

It’s an intriguing question @indio02

And I don’t think there are likely to be any clear or definitive answers, because so many factors involved.

A few snippets to add into your pondering…

HbA1c is a sort of long-term ‘proxy measure’ for general glucose concentrations. The more glucose that has been circulating during the lifespan of your red blood cells (approx 120 days) the more opportunity there is for some of them to be glycosylated. A one-way change that can be observed by measuring the amount of A1c among your haemoglobin (Hb). As old red blood cells get re-absorbed, and new ones are created to replace them, you get a sort of ‘rolling total’. Not all red blood cells last the full 120 days, so the figure is ‘weighted’ towards more recent weeks.

HbA1c has been measured for many years in clinical studies. And significant pieces of work (like DCCT and UKPDS) have found that diabetes complications are more common among people with higher HbA1c, particularly over longer timeframes, so targets encouraging lower Hba1cs were implemented to try to reduce risk. But again this is complicated, and multi-factorial, and two people might have an identical HbA1c, and the same diabetes duration, and one person may get complications while the other does not. This is biology and risk, not mathematics and formulae.

For T1s, the International Consensus on Time In Range suggested that people using CGM should aim for 70%+ of time between 4-10, and as losss possible, but no more than 4% of time below 4.0. So for T1s the guidance allows 25% of the day above 10mmol/L with the expectation that this would still give an on-target HbA1c of around 48mmol/mol.

Lastly, HbA1c is not a simple complications-busting trump card. Research shows that two people can get identical HbA1c. One from a gently meandering glucose profile mostly in range, with low glucose instability (number of wobbles), and glucose variation (extent of wobbles). The other from dramatically varying glucose profiles low to high and back again. They would have very different levels of risk. Low HbA1c offers less protection if the glucose instability and variation are high. Stability seems very helpful, John Walsh (Pumping Insulin) cited research that showed that staying steadily and consistently at 20mmol/L while not ideal, actually had less risk of retinopathy than someone lurching from say 2 to 15 and back again all day every day.

My basic understanding is that a few wobbles are OK, but in general the more gentle you can get your rises and falls of glucose to be, and within as narrow a range as you can, are likely to offer you lowest risk.

No idea if any of that will help!