BG to HbA1c conversion

[AM1874]

Earlier today, looking for information to answer an interesting question from @wiseowl_123 , I found a post on the forum describing how HbA1c is calaculated from BG readings . This includes a converter which I have used to calculate my own readings as follows ..

I have been testing my Fasting, pre-Prandial and post-Prandial levels every day since 22nd Feb. I have now averaged all these readings, applied the converter and come up with ..

Fasting : 5.63 average reading .. converts to HbA1c of 32.8
Pre- Pr : 5.59 average reading .. converts to HbA1c of 32.5
Post-Pr : 5.75 average reading .. converts to HbA1c of 33.6

I am, of course, delighted with this but I am a little unsure about the accuracy of these calculations and the overall reliability of the converter. I would really appreciate comments, advice etc from anybody who has used this ..

 

[Jamesuk9]

If your readings are consistent and your meter is reasonably accurate, then the total average is pretty much spot on in most instances.

I calculated 5.3 a1c over 90 days from my meter readings, 5.3 is what the result was just yesterday.

 

[AM1874]

If your readings are consistent and your meter is reasonably accurate, then the total average is pretty much spot on in most instances.

I calculated 5.3 a1c over 90 days from my meter readings, 5.3 is what the result was just yesterday.

Hi @Jamesuk9 .. thanks, that's very encouraging. At the moment, I'm trying to dig a bit more deeply into this .. see my following post

 

[AM1874]

As said in my post above, I have been testing my Fasting, pre-Prandial and post-Prandial levels every day since 22nd Feb. I have used either / both the TEE2 and the SD Codefree meters for both actual results and for comparative purposes. I have never found a difference of more than 0.1 mmol between the two meters

I have now summarised and averaged all these readings, applied the converter and come up with ..

Fasting : 49 Readings : Highest 6.3 : Lowest 5.1 : Average 5.63 .. converts to HbA1c of 32.8
Pre- Pr : 83 Readings : Highest 6.3 : Lowest 4.9 : Average 5.59 .. converts to HbA1c of 32.5
Post-Pr : 79 Readings : Highest 6.4 : Lowest 5.1 : Average 5.75 .. converts to HbA1c of 33.6

I am, of course, delighted with this but I have a few questions ..
# assuming that my meter readings are accurate, does this carry over to the HbA1c conversions?
# if conversions are accurate what does this mean in terms of my current diabetic status? (non, pre or still T2)
# I do not have a review until early June .. should I be informing my GP of these readings and conversions?
# do I need to continue with my meds? .. 2 x 500g Metformin and 1 x 10 Atorvastatin .. (I currently intend to)
# if I continue with LCHF and exercise as now, are these figures likely to be permanent or just temporary?

I am aware that some of these questions may appear pretty obvious but this has put me on a real high and I am trying to find out if I should be preparing for a crash around the corner. I really would appreciate any comments, advice or info from anybody who has used the converter ..

 

[Avocado Sevenfold]

Is there a difference when comparing capillary vs venous blood for calculating hba1c?

 

[AM1874]

Is there a difference when comparing capillary vs venous blood for calculating hba1c?

Not mentioned on the page that describes the relationship between HbA1c and BG .. what it does say is that ..
"It’s important to note that HbA1c and blood glucose tests measure different things.
Blood glucose tests measure the concentration of glucose molecules in the blood at a single point in time.
The HbA1c test measures the proportion of haemoglobin molecules in the blood that have become chemically bonded with glucose over a period of up to 3 months."
http://www.diabetes.co.uk/hba1c-to-blood-sugar-level-converter.html

 

[Jamesuk9]

@AM1874 my meter readings were obtained using Tee2, it proved more accurate and consistent than my accucheck mobile which clearly was reading a bit low.

All you need is an average of ALL readings for the past 90 days, the tee2 does this for you in the meter memory and then convert to hba1c.

You'll find little difference between what the tee2 conversion from average is telling you and the actual venous a1c at the doctors.

It would appear if you have meticulously taken readings then your numbers indicate control, reversal, whichever you wish to call it.

Congratulations!

 

[Jamesuk9]

Is there a difference when comparing capillary vs venous blood for calculating hba1c?

Yes, all meters sold in UK now convert to plasma equivalent though, they do not read capillary.

So assuming you have a current meter that is converting to plasma equivalent, you can use the average to calculate a1c.

 

[Avocado Sevenfold]

Yes, all meters sold in UK now convert to plasma equivalent though, they do not read capillary.

So assuming you have a current meter that is converting to plasma equivalent, you can use the average to calculate a1c.

Ah I see. I didn't know that, thanks.

I think home testing is a good guide, but for an accurate hba1c, it is best left to the lab, especially as I have often read that the latter weeks have more bearing on the result than earlier weeks.

 

[Jamesuk9]

Ah I see. I didn't know that, thanks.

I think home testing is a good guide, but for an accurate hba1c, it is best left to the lab, especially as I have often read that the latter weeks have more bearing on the result than earlier weeks.

Yes, you're not wrong.... Testing several times a day continuously is very close though when calculated. In my case and in many others it was spot on.

The only real variation could occur if your red cell life differs from what they consider the norm.

 

[AM1874]

Thank you @Jamesuk9 and @Avocado Sevenfold .. I really appreciate your input

 

[Avocado Sevenfold]

....I have often read that the latter weeks have more bearing on the result than earlier weeks.

The third paragraph here might explain this better. I don't speak "science". Good luck!

http://jcp.bmj.com/content/53/5/335.full

 

[AM1874]

@AM1874 my meter readings were obtained using Tee2, it proved more accurate and consistent than my accucheck mobile which clearly was reading a bit low.

All you need is an average of ALL readings for the past 90 days, the tee2 does this for you in the meter memory and then convert to hba1c.

You'll find little difference between what the tee2 conversion from average is telling you and the actual venous a1c at the doctors.

It would appear if you have meticulously taken readings then your numbers indicate control, reversal, whichever you wish to call it.

Congratulations!

I have always tried to be meticulous with taking and recording my readings (I'm a bit old-school and prefer a spreadsheet) ..

I have followed a strict LCHF lifestyle (< 40g daily), and increased my exercise to every day .. but is control, reversal whatever really possible from a diagnosis of 12.4 HbA1c and 12.5 BG less than 2 months ago?

PS: sorry for hassling but this all made me pretty hyper

 

[AM1874]

The third paragraph here might explain this better. I don't speak "science". Good luck!

http://jcp.bmj.com/content/53/5/335.full

Gotcha .. thanks

 

[Jamesuk9]

I have always tried to be meticulous with taking and recording my readings (I'm a bit old-school and prefer a spreadsheet) ..

I have followed a strict LCHF lifestyle (< 40g daily), and increased my exercise to every day .. but is control, reversal whatever really possible from a diagnosis of 12.4 HbA1c and 12.5 BG less than 2 months ago?

PS: sorry for hassling but this all made me pretty hyper

Yes mate, unless you have a seriously dodgy meter, which is unlikely, it seems you've well and truly got it under control.

In your shoes I'd be hassling the surgery to have the review brought forward to confirm.

Cured is debatable, but I know you said you intend to continue LC for life so in that case pat yourself on the back as you've done the hard work and can now relax a bit.

Really is impressive the way you've take D by the scruff and dealt with it.

 

[AM1874]

Thank you @Jamesuk9 .. I really appreciate that .. and I will contact my surgery to see about rescheduling my review

 

[bulkbiker]

I have always tried to be meticulous with taking and recording my readings (I'm a bit old-school and prefer a spreadsheet) ..

I have followed a strict LCHF lifestyle (< 40g daily), and increased my exercise to every day .. but is control, reversal whatever really possible from a diagnosis of 12.4 HbA1c and 12.5 BG less than 2 months ago?

PS: sorry for hassling but this all made me pretty hyper

In the way you have taken control I would say its very likely that you are well out of the pre-diabetes range - the effects of diet can be very swift especially if you have cut carbs dramatically as you have. Also of course you are still taking the pills so that will have had a minor impact as well. You're doing an amazing job well done!

 

[Mr_Pot]

Hi @AM1874 Your readings are most impressive especially the postprandial which have very little variation, do you eat the same thing at every meal? You really do seem to have achieved excellent control, it would be interesting to know what happened if you now had something high carb like mashed potato. Regarding the Hba1c, it is of course not an average BG level, but an indicator of an average BG level. In your case because your readings are so consistent there is probably a good correlation but for someone with a big variation it would be necessary to derive the average from say hourly readings day and night to accurately predict Hba1c.

 

[Jamesuk9]

In my personal experience, it required around 15 readings a day to provide an accurate representation. I too have little variation though, at most 1 mmol/L at one hour post prandial and back at baseline around 2 hours when low carbing.

That said, there are many people here whose a1c matched their average meter reading conversions.

It's certainly a reasonably accurate indicator of the big picture for sure, that is why we do it of course.

Control is there for those who want to work at it, that is pretty much indisputable.

 

[NoCrbs4Me]

According to my Freestyle Libre, my HbA1c should be 28 mmol/mol, but the lab results are usually around 39 mmol/mol. I must be a high glycator or my red blood cells live longer than an average person's.