A1C cut-point to avoid diabetic complications

[finsit]

What is the optimal level of a1c (blood glucose) to avoid or reduce diabetic complications?

As a newly diagnosed diabetic, the first question comes to the mind how fast I am going to get complications; or, whether keeping my BG in range, can I avoid or delay these complications; or what’s the cut point in terms of a1c or BG levels for a smooth sailing?

Well, I have been going through 10s of research study and papers recently, some as old as 20 years but then I started searching for more recent articles just to make sure I am updated on the information.

I highly recommend three books that if you have in your library, you will not need anything else to understand all the concepts about diet, metabolic disorder and diabetes and how to keep yourself healthy, or manage if you already have the metabolic disorder. These are;

• Diabetic Solution by Dr. Richard K. Bernstein
• Protein Power by Dr. Michael Eades
• The Art and Science of Low Carbohydrate Living by Jeff Volek

Of course, reading all the research papers and diabetic journals will keep you updated and let you understand more the decades of hard-work put in the above three books.

The quick answer to why diabetic complications happen is the oxidative stress and glycation or AGEs (Advanced Glycation End-products). AGEs are happening in the human body consistently whether you are diabetic or non-diabetic, it’s a continuous process and you can not stop it. However, the level of AGEs production in your body depends upon how high and for how long your blood glucose has been high. The higher the BG and the longer they have been in a higher range, the more AGEs will be produced. If your blood sugar is mostly within the normal range 80-85 mg/dl, your AGEs production will be just normal (so basically you will age like Royals). Relationship of AGEs and complication is U-shaped. So below the normal or above the normal range, your AGEs production will be imbalanced. If you have had high BGs, you are producing more AGEs and hence you will have more complications because of glycation (excessive sugar attaching to your protein). Because this glycation mainly happens at the end points of neuron, it always affect eyes, kidneys, arteries, feet etc. It’s not as simple as it looks because there are lot more processes involved when you have more AGEs in the body that change your mitochondria and cell structure which ultimately produces calcification in arteries leading to cardiac abnormalities.

The bottom line is that more the blood sugar and for longer it stays on higher levels, you will have more AGEs and more diabetic complications. AGEs production in diabetic is 60% more than non-diabetic according to the book BloodSugar101 and that makes sense. The less AGEs you produce the better your chances are to avoid diabetic complications and that is a result of near normal sugars around the clock.

This research study from 2012 shows that the chronic complications were least below the a1c of 6%.

https://www.researchgate.net/public...nd_chronic_complications_in_diabetes_mellitus

This is another interesting study of a1c correlation with diabetic complications which shows that an a1c value below 6% is the safe value to target for.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114320/

This is perhaps a more interesting study about diabetic retinopathy occurrence at different FPG and A1C levels. Its evident that prevalence of diabetic retinopathy starts when the FPG starts increasing above 5.5 mmol/l level, or when your PPG starts increasing from 9 mmol/l level, or at HBA1C level of 5.5 which seems like a cut point in this study.

Full study is here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3005450/

I could only find the reference to retinopathy complications, but in another study where the researcher correlated neuropathy and CVD as well, the threshold seems to be the same.

My conclusion (and the goals that I would set for myself) after all those months of research is as follows:

1. Try to keep your A1C as close to 5% as possible
2. Try to keep your fasting BG below 5.5 mmol/l
3. Try to keep your post prandial peak below 7 mmol/l

I know it’s a lot to ask and its really hard to maintain above levels particularly if you are not taking insulin for D2, but the least you should be able to do is to keep 80% of your time in range TIR between 70-120 mg/dl.

Its important to mention that AGEs are not only produced by glycation but can also be added to your body through dietary sources through what is called Maillard reaction or dAGE, however most of these dietary AGEs are excreted from the body and daily limit of dietary AGEs recommended per day is 15000 units/day (or kU/gm), which sounds very high but just a 90 gm pan fried beef steak contains over 8500 of these units.

A safe and optimal dAGE intake for the purposes of disease prevention has yet to be established. However, in animal studies, a reduction of dAGE by 50% of usual intake is associated with reduced levels of oxidative stress, less deterioration of insulin sensitivity and kidney function with age, and longer life span.

Reducing dAGE may be especially important for people with diabetes, who generate more endogenous AGEs than those without diabetes and for those with renal disease, who have impaired AGE clearance from the body

Its very interesting and a relatively new concept but if you really need to read more details about it, here is a full guide including which food has how many AGEs and what type of cooking methods increase or decrease these AGEs.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3704564/

I would be very interested to hear more about your personal experiences with your glycaemic control, number of years of diabetes and any complications that developed or reversed.

 

[SueJB]

!

 

[Ronancastled]

I was diagnosed with an A1c of 6.9(52) and background retinopathy was picked up on my first scan. The following year got my A1c back to 5.2(33) and the eye test came back all clear.

 

[Goonergal]

!

Sue, it’s not clear what point you’re trying to make.

 

[Rokaab]

My conclusion after all those months of research is as follows:

1. Try to keep your A1C as close to 5% as possible
2. Try to keep your fasting BG below 5.5 mmol/l
3. Try to keep your highest post prandial peak below 7 mmol/l

I know it’s a lot to ask and its really hard to maintain above levels particularly if you are not taking insulin for D2, but the least you should be able to do is to keep 80% of your time in range TIR between 70-120 mg/dl.

Whilst I realise you have put I a lot of research into this, you must remember there are also many T1's (and various other types taking insulin) on these forums who must take insulin, where striving for an HbA1c like that would just be dangerous and lead to a lot of hypos for many.

I'm not saying that the findings are wrong (I cant say whether they are wrong or right) just that for some of us it would be dangerous to try and get to those levels.

Or were you not aiming this all diabetics?

 

[Mbaker]

Complications can and do happen in those with pre-diabetes. Like the book recommendations, as they are older, but as they were accurate the message is perfect still.
I would opt for the very best results I could achieve and not rely on someone elses findings, which may not apply to me.

 

[finsit]

Whilst I realise you have put I a lot of research into this, you must remember there are also many T1's (and various other types taking insulin) on these forums who must take insulin, where striving for an HbA1c like that would just be dangerous and lead to a lot of hypos for many.

I'm not saying that the findings are wrong (I cant say whether they are wrong or right) just that for some of us it would be dangerous to try and get to those levels.

Or were you not aiming this all diabetics?

Hi thanks for the input. My personal opinion is that what's normal is normal whether its for a T1, T2 or a non-diabetic. Interestingly, i have been testing my friends and family and many of them have higher reading than i suggested above. Few months ago, i didnt know whats normal and whats not. But now with the CGMs and lot of actual readings on the internet that you can find, these levels are perfectly fine. For T1, in my opinion, it might be easier to keep their BGs most part of the day in the time in range (TIR), that i suggested towards the end. I may be a little biased because i myself am T2 and i do not understand how difficult it is for T1s to manage their blood sugars. But i must say the use of "laws of small numbers" should solve lots of issue in DM management. Hypo's will only happen if there is a lot of carbs and lot of insulin which never match each other. There are again a lot of studies that prove that hypos happen mainly on high-carb diet.

However, we all are humans and we can not just keep looking at the forbidden food around and not indulge in the party some time . What i said is not a medical opinion and is based on the research i did and my personal opinion particularly for those who are newly diagnosed and don't have time to stay 18 hours on computer to dig into research papers to get their answers. If something works for someone, i would think i did my job.

My main interest to start this topic is to get feedback of other people for the length of their DM and any complication or reversal. I appreciate @Ronancastled input for the personal experience.

One thing i forgot to mention that these readings where i think we diabetics have the best chance for not having any complications, but everyone is different. There maybe people who are above 6 or 7% and they are still living a healthy life, depending upon the genes, severity of the disease, BMI and their physical activity level.

 

[Grant_Vicat]

Hi thanks for the input. My personal opinion is that what's normal is normal whether its for a T1, T2 or a non-diabetic. Interestingly, i have been testing my friends and family and many of them have higher reading than i suggested above. Few months ago, i didnt know whats normal and whats not. But now with the CGMs and lot of actual readings on the internet that you can find, these levels are perfectly fine. For T1, in my opinion, it might be easier to keep their BGs most part of the day in the time in range (TIR), that i suggested towards the end. I may be a little biased because i myself am T2 and i do not understand how difficult it is for T1s to manage their blood sugars. But i must say the use of "laws of small numbers" should solve lots of issue in DM management. Hypo's will only happen if there is a lot of carbs and lot of insulin which never match each other. There are again a lot of studies that prove that hypos happen mainly on high-carb diet.

However, we all are humans and we can not just keep looking at the forbidden food around and not indulge in the party some time . What i said is not a medical opinion and is based on the research i did and my personal opinion particularly for those who are newly diagnosed and don't have time to stay 18 hours on computer to dig into research papers to get their answers. If something works for someone, i would think i did my job.

My main interest to start this topic is to get feedback of other people for the length of their DM and any complication or reversal. I appreciate @Ronancastled input for the personal experience.

One thing i forgot to mention that these readings where i think we diabetics have the best chance for not having any complications, but everyone is different. There maybe people who are above 6 or 7% and they are still living a healthy life, depending upon the genes, severity of the disease, BMI and their physical activity level.

If it helps I had Type 1 diagnosed at 11 months in 1959. In 1966 I had a 5 day coma. Put on a slow and fast acting mix twice a day instead of 1 dose of slow acting a day Also put on the Lawrence Line weight diet (240g Carbohydrate a day). Passing proteins in 1973. Photo-coagulation in both eyes from 1979-1983. Given a glucometer by King's College Hospital in 1979 and thus my control improved dramatically. Kidney function deterioration considerably slowed. 2000 put on restricted protein diet (still on 240g of Carbohydrate) and phosphate binders a few years later. Never went on dialysis but had kidney/pancreas transplant in 2013. I still eat 240g Carbs a day and weigh 71kg, exactly the same as in 1980.

 

[RICK-59]

As a newly diagnosed diabetic, the first question comes to the mind how fast I am going to get complications; or, whether keeping my BG in range, can I avoid or delay these complications; or what’s the cut point in terms of a1c or BG levels for a smooth sailing?

Well, I have been going through 10s of research study and papers recently, some as old as 20 years but then I started searching for more recent articles just to make sure I am updated on the information.

I highly recommend three books that if you have in your library, you will not need anything else to understand all the concepts about diet, metabolic disorder and diabetes and how to keep yourself healthy, or manage if you already have the metabolic disorder. These are;

• Diabetic Solution by Dr. Richard K. Bernstein
• 
  
• Protein Power by Dr. Michael Eades
• 
  
• The Art and Science of Low Carbohydrate Living by Jeff Volek

Of course, reading all the research papers and diabetic journals will keep you updated and let you understand more the decades of hard-work put in the above three books.

The quick answer to why diabetic complications happen is the oxidative stress and glycation or AGEs (Abnormal Glycation End-products). AGEs are happening in the human body consistently whether you are diabetic or non-diabetic, it’s a continuous process and you can not stop it. However, the level of AGEs production in your body depends upon how high and for how long your blood glucose has been high. The higher the BG and the longer they have been in a higher range, the more AGEs will be produced. If your blood sugar is mostly within the normal range 80-85 mg/dl, your AGEs production will be just normal (so basically you will age like Royals). Relationship of AGEs and complication is U-shaped. So below the normal or above the normal range, your AGEs production will be imbalanced. If you have had high BGs, you are producing more AGEs and hence you will have more complications because of glycation (excessive sugar attaching to your protein). Because this glycation mainly happens at the end points of neuron, it always affect eyes, kidneys, arteries, feet etc. It’s not as simple as it looks because there are lot more processes involved when you have more AGEs in the body that change your mitochondria and cell structure which ultimately produces calcification in arteries leading to cardiac abnormalities.

The bottom line is that more the blood sugar and for longer it stays on higher levels, you will have more AGEs and more diabetic complications. AGEs production in diabetic is 60% more than non-diabetic according to the book BloodSugar101 and that makes sense. The less AGEs you produce the better your chances are to avoid diabetic complications and that is a result of near normal sugars around the clock.

This research study from 2012 shows that the chronic complications were least below the a1c of 6%.

View attachment 48164

https://www.researchgate.net/public...nd_chronic_complications_in_diabetes_mellitus

This is another interesting study of a1c correlation with diabetic complications which shows that an a1c value below 6% is the safe value to target for.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3114320/

This is perhaps a more interesting study about diabetic retinopathy occurrence at different FPG and A1C levels. Its evident that prevalence of diabetic retinopathy starts when the FPG starts increasing above 5.5 mmol/l level, or when your PPG starts increasing from 9 mmol/l level, or at HBA1C level of 5.5 which seems like a cut point in this study.

Full study is here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3005450/

View attachment 48165

I could only find the reference to retinopathy complications, but in another study where the researcher correlated neuropathy and CVD as well, the threshold seems to be the same.

My conclusion after all those months of research is as follows:

1. Try to keep your A1C as close to 5% as possible
2. Try to keep your fasting BG below 5.5 mmol/l
3. Try to keep your highest post prandial peak below 7 mmol/l

I know it’s a lot to ask and its really hard to maintain above levels particularly if you are not taking insulin for D2, but the least you should be able to do is to keep 80% of your time in range TIR between 70-120 mg/dl.

Its important to mention that AGEs are not only produced by glycation but can also be added to your body through dietary sources through what is called Maillard reaction or dAGE, however most of these dietary AGEs are excreted from the body and daily limit of dietary AGEs recommended per day is 15000 units/day (or kU/gm), which sounds very high but just a 90 gm pan fried beef steak contains over 8500 of these units.

A safe and optimal dAGE intake for the purposes of disease prevention has yet to be established. However, in animal studies, a reduction of dAGE by 50% of usual intake is associated with reduced levels of oxidative stress, less deterioration of insulin sensitivity and kidney function with age, and longer life span.

Reducing dAGE may be especially important for people with diabetes, who generate more endogenous AGEs than those without diabetes and for those with renal disease, who have impaired AGE clearance from the body

Its very interesting and a relatively new concept but if you really need to read more details about it, here is a full guide including which food has how many AGEs and what type of cooking methods increase or decrease these AGEs.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3704564/

I would be very interested to hear more about your personal experiences with your glycaemic control, number of years of diabetes and any complications that developed or reversed.

Sorry to hear you have been diagnosed with diabetes, I remember that it was a shock to my system but I learnt to live with it.

I was diagnosed in 2010, I can't remember what level my a1c was but it was bad, off the shart and I think the shart that the DN uses goes up to 100.

I was put on one metformin SL 500 and attended a diabetes seminar once a week for a month. I changed my diet, lost 10kg and substantially increased my exercise routine in that month; for the next 6 months more of the same. The next a1c was normal and I was taken off the tablet.

I made the mistake to relax my diet and incorporate bread, pasta and rice to normal quantities, having said that, my a1c for the following 4 years was in the green zone or < 48

On the 5th year I was diagnosed with Atrial Fibrillation, doctors couldn't tell me how long I've had it since I don't get any symptoms so it's possible that I had it before diabetes, never stopped me from putting my body through intensive training. Doctors said I had to change my exercise routine.... basically slow down my cycling drastically, for some reason cycling with an eye on my heart rate became boring and I couldn't motivate myself to go out as much, diabetes came back soon after and since then I piled on the weight and the tablets. During the first lock down I lost 4kg and I thought I was doing really well, apart from feeling very tired all the time, I blame the lockdown and the lack of activities.... every Saturday I was out with my cycling club doing in excess of 50 miles, before the lockdown... in August 2020 I was invited for a blood test and my a1c came back at at 135 or 14.5 in American money. I was already on 4 metformin so the DN added 2 glicazide 80mg. After a month or so I began to look for an alternative treatment or something else to add that could make a difference.... I had listened to the advice and I was adding more tablets every year. I found videos on low carb and intermittent fasting on youtube and began to try out some of the advice, I had nothing to lose, after a week I was doing OMAD and dropping a tablet per week, after 6 weeks I had lost 14kg and I was free of tables for many years.... my energy levels were back to normal so I started doing a lot of work around the house and cycling which helped with the weight loss. In December 3rd I has my last a1c and it was 47 and it should be lower now.

That's my life as a diabetic type 2, you can reverse diabetes following the correct advice.
I'm not sure my Atrial Fibrillation was caused by the diabetes, it's possible though. My eyes are OK but my kidneys are suffering with the diabetes... I have to take tablets to protect them. My libido has never been a problem, not even when my sugar level was so high.... although my eyes took a pounding then, I was worried that my vision became blurry but it's back to normal now and the eye test for diabetics didn't pick any damage.

I wish someone told me years ago that the cause of my diabetes was insulin resistance and that snacking made the problem worse.... I never saw anything wrong with picking a few grapes, an apple, a biscuit, etc throughout the day since I was a child, my snacks weren't large but were many and every time I snacked my pancreas released more insuline until I became insulin resistant.... too many years of abuse.

Low carb diet and intermittent fasting is my new way of life now, I got used to it.

I hope that helps but if I were you I wouldn't worry too much about what complications you might get in the future, simply try to learn how to keep your glucose level in the green zone.

Good luck

 

[Rokaab]

My main interest to start this topic is to get feedback of other people for the length of their DM and any complication or reversal.

In which case:
Time with Diabetes:: virtually 44 years - no idea what the HbA1c's were before I was 16 , I don't think they did them back then - but until I hit the age of 42 it was never below 53 (7%) and at times was considerably higher (my a-level years were about 90ish (10.4%ish).

Complications:

• background retinopathy - with the occasional maculopathy turning up ever since my HbA1c's got better than 53(7%) .....
• pessimism
• grumpiness
• lipohypertrophy
• nothing else - apart from other immune system diseases, everything else is fine

Mine has always been really tricky to deal with, it never seems to behave - even my new pump with auto-mode is having problems!
Edit: my HbA1c is now at 45 (6.3%) and is the best its ever been, any lower would just be dangerous for me

 

[Antje77]

Hypo's will only happen if there is a lot of carbs and lot of insulin which never match each other.

Not true.

I may be a little biased because i myself am T2 and i do not understand how difficult it is for T1s to manage their blood sugars.

Agree.
And the same goes for T2's on insulin.

 

[UK T1]

Hi, just to second @Antje77 post above. My understanding is that an HbA1c of 6% is borderline diabetic, so it makes complete sense that the research finds fewer complications arise with a non-diabetic HbA1c. There will always be an element of 'luck' and interaction with other health conditions and lifestyle too.

Unfortunately type 1 diabetics cannot safely strive for such low HbA1c values over prolonged periods of time. As mentioned it risks the person losing their symptoms of low blood glucose, which can be fatal for a type 1.

I would suggest this thread is most useful for you/your research and questions you have if you focus on type 2 diabetics not on insulin?

 

[zand]

Atrial fibrillation can be caused by doing extreme physical activity whilst being low on magnesium. Of course that's not the only cause, but I am quite sure in my own mind that's what caused mine.

 

[becca59]

@zamalik with the best will in the world, managing the use of injected insulin is extremely complex and difficult. With respect, it is not just the correlation between what is eaten and amounts injected. If it was that easy, the majority of type 1 posters on this forum would have a very low HBA1C due to the amount of work they put into this exercise every single day.
As many of us type 1s sometimes joke, the only reason for their mad high sugars that day must be due to their temerity to wear green socks!

 

[Brunneria]

I think that living with glucose dysregulation, whether that is being Type1, Type2, 3c, MODY, having reactive hypoglycaemia, or any of the other varieties, is rather like spinning plates.

Taking the HbA1c as a standard measurement is nice and cheap for health care organisations, and it is relatively quick and easy to do (one quick blood test every few months), but all it does is give a tiny glimpse into what is really going on.
- and what goes on is fundamentally different for each type of D, and each person within that type.

For example:
A T1 might be having massive swings in blood glucose, another might have very steady numbers each and every day. They both have the same HbA1c, yet have quite different risks of developing diabetic complications.
Meanwhile, one T2 may have consistently low blood glucose, achieved by medication and a very active exercise regime. Another T2 may do no exercise at all, and maintain their blood glucose stability by ketogenic eating. Again, both have the same HbA1c, yet how do we compare their risks?

In each of those cases, the HbA1c tells us very little about what is really going on, and what the odds of complications really are.

Another factor is how long ago the person was diagnosed, how they were diagnosed, and what their historic bg levels have been.

So many people, of all types of D experience burnout, low and high periods, etc. etc. and that all factors into their long term risk.

Sometimes T1 starts slowly (LADA) which may result in a slow diagnosis and sustained high levels for years before the problem is identified. Or they are wrongly diagnosed T2 and left on inappropriate medication for a long period. Or a T1 becomes ill so suddenly that they develop life threatening ketoacidosis and are hospitalised. Both of those may (please note I am saying may) impact their later risk of complications. Until someone does a series of studies with a lot of T1s, we won't have a definitive answer on that. If anyone know of such studies, I would love to read them.
Meanwhile, a T2 may not be diagnosed until 5 or 10 years after their blood glucose rises to problematic levels. Or the diagnosis may be made at a very early stage, and they may have dramatically different levels of insulin resistance.

In my opinion, HbA1c is a helpful shorthand (and sometimes it is the only shorthand we are offered), but it is of very limited value in predicting very much at all.

 

[finsit]

I was diagnosed with an A1c of 6.9(52) and background retinopathy was picked up on my first scan. The following year got my A1c back to 5.2(33) and the eye test came back all clear.

Thank you for sharing this. Did they have to treat you for background retinopathy or it went on its own after normalising the BG?

 

[finsit]

If it helps I had Type 1 diagnosed at 11 months in 1959. In 1966 I had a 5 day coma. Put on a slow and fast acting mix twice a day instead of 1 dose of slow acting a day Also put on the Lawrence Line weight diet (240g Carbohydrate a day). Passing proteins in 1973. Photo-coagulation in both eyes from 1979-1983. Given a glucometer by King's College Hospital in 1979 and thus my control improved dramatically. Kidney function deterioration considerably slowed. 2000 put on restricted protein diet (still on 240g of Carbohydrate) and phosphate binders a few years later. Never went on dialysis but had kidney/pancreas transplant in 2013. I still eat 240g Carbs a day and weigh 71kg, exactly the same as in 1980.

You are definitely a fighter and a survivor. Thanks for sharing, seems you went through a lot!

 

[finsit]

In which case:
Time with Diabetes:: virtually 44 years - no idea what the HbA1c's were before I was 16 , I don't think they did them back then - but until I hit the age of 42 it was never below 53 (7%) and at times was considerably higher (my a-level years were about 90ish (10.4%ish).

Complications:

• background retinopathy - with the occasional maculopathy turning up ever since my HbA1c's got better than 53(7%) .....
• pessimism
• grumpiness
• lipohypertrophy
• nothing else - apart from other immune system diseases, everything else is fine

Mine has always been really tricky to deal with, it never seems to behave - even my new pump with auto-mode is having problems!
Edit: my HbA1c is now at 45 (6.3%) and is the best its ever been, any lower would just be dangerous for me

Thank you for sharing your personal experience and definitely two thumbs up for keeping it at 6.3% after all these years. I understand its easy to achieve close to 6% during the honeymoon period or at the start but as we all know its a marathon and you need to put up with it for long. Appreciate your response.

 

[Ronancastled]

Thank you for sharing this. Did they have to treat you for background retinopathy or it went on its own after normalising the BG?

Luckily no, I believe it's the first stage & the advice was to control my glucose & BP.

 

[finsit]

I think that living with glucose dysregulation, whether that is being Type1, Type2, 3c, MODY, having reactive hypoglycaemia, or any of the other varieties, is rather like spinning plates.

Taking the HbA1c as a standard measurement is nice and cheap for health care organisations, and it is relatively quick and easy to do (one quick blood test every few months), but all it does is give a tiny glimpse into what is really going on.
- and what goes on is fundamentally different for each type of D, and each person within that type.

For example:
A T1 might be having massive swings in blood glucose, another might have very steady numbers each and every day. They both have the same HbA1c, yet have quite different risks of developing diabetic complications.
Meanwhile, one T2 may have consistently low blood glucose, achieved by medication and a very active exercise regime. Another T2 may do no exercise at all, and maintain their blood glucose stability by ketogenic eating. Again, both have the same HbA1c, yet how do we compare their risks?

In each of those cases, the HbA1c tells us very little about what is really going on, and what the odds of complications really are.

Another factor is how long ago the person was diagnosed, how they were diagnosed, and what their historic bg levels have been.

So many people, of all types of D experience burnout, low and high periods, etc. etc. and that all factors into their long term risk.

Sometimes T1 starts slowly (LADA) which may result in a slow diagnosis and sustained high levels for years before the problem is identified. Or they are wrongly diagnosed T2 and left on inappropriate medication for a long period. Or a T1 becomes ill so suddenly that they develop life threatening ketoacidosis and are hospitalised. Both of those may (please note I am saying may) impact their later risk of complications. Until someone does a series of studies with a lot of T1s, we won't have a definitive answer on that. If anyone know of such studies, I would love to read them.
Meanwhile, a T2 may not be diagnosed until 5 or 10 years after their blood glucose rises to problematic levels. Or the diagnosis may be made at a very early stage, and they may have dramatically different levels of insulin resistance.

In my opinion, HbA1c is a helpful shorthand (and sometimes it is the only shorthand we are offered), but it is of very limited value in predicting very much at all.

Thank you for the valuable feedback and completely agreed. I completely understand that a1c is just a broad measure of how you have been performing and i mainly see it as how much AGEs you have been producing regardless of the lows and highs. That is the reason i mentioned time in range TIR which has been getting quite a lot of traction recently and is a better measure of seeing how flat your glycaemic curve has been. This article is a good resource for anyone who would like to read more about the recent research on TIR https://diatribe.org/time-range

As you can see from the image below, as you mentioned, an a1c of 7% can have so much varying BGs in three different situations. However, my point here is that these variations become so obvious only when you are a1c level is high enough to give these readings like 7%. But if we are talking of cut-point to avoid complications and measuring it at lets say 5.2%, the variations in the below diagram wont be as big as they are at 7%.