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CGM Vs hba1c

R

rfenwick

Newbie
Messages
3
Type of diabetes
Type 2
Treatment type
Diet only
I'm newly diagnosed T2, with hba1c of 50, and have not yet had my first diabetes clinic appointment.

I've read the info for newly diagnosed on the forum, and the recommended NICE ranges.

Being very data driven I decided to try out a Libre 2 while I wait for the clinic. After a few days it is saying I have spent 92% of the time in the app's default "OK" range of 3.9 - 10 mmol, with the highest recorded reading at 13.

My newby question is - is there some kind of multiplier involved in calculating the hba1c? I've made some modest diet changes but nothing huge yet. Can numbers in this range lead to an hba1c of 50? I keep reading that the hba1c is an 'average' of 3-6 months

Should probably just be a patient patient and wait for the clinic, but your advice very welcome. Thanks!
 
Last edited:
The app typically gives an indication of hba1c but needs about 3 weeks of data before it can do that

And it’s only a rough indication
 
The app shows the estimated A1c in the menu. Most find it on the low side.

Also if you search here you will find an online calculator.

HTH
 
barrym said:
The app shows the estimated A1c in the menu. Most find it on the low side.

Also if you search here you will find an online calculator.

HTH
Click to expand...
Aha, thank you, the calculator answers my question
 
Libre is a good way to get a clearer understand of where you are daily. Just be warned that when they start to show large increases in glucose it will not be as accurate. My libre is reading 11.6 at moment but a finger prick is showing 15.3. Other than on rapid increases is normally showing the same as the finger prick
 
barrym said:
The app shows the estimated A1c in the menu. Most find it on the low side.

Also if you search here you will find an online calculator.

HTH
Click to expand...
For info I find my Libre 2 reading to be higher than the surgery blood test. Perhaps the way Libre calculates it depends on the wearer BS profile?
 
I find the Estimated HBA1C to be another metric you can track to show the Overall trend of our diabetes management.
For me, it is a constant 10 lower than the blood test so I do not consider it a useful representation of HbA1C.
 
rfenwick said:
Can numbers in this range lead to an hba1c of 50?
Click to expand...
An hba1c of 50mmol/mol means that your average blood glucose has likely been around 8.8mmol/l, so yes, this is very well possible.
The preset range on Libre is meant for T1's on insulin, a non diabetic wouldn't often hit the higher part of the range, and when they do it would only be for a short while.

While Libre is an amazing tool for finding trends and patterns, it's not as good when it comes to absolute numbers. For some, it reads mostly spot on compared with a fingerprick, but many others find that Libre reads consistently lower or higher than a fingerprick.
For me it reads lower, and thus the estimated hba1c has been 8mmol/mol lower than my lab tests for years.
 
Hi @rfenwick and welcome to the forum.

Just in case you don't already know, the HbA1C test shows the average glycation of your red blood cells over their life (approx 3 months). So it can only really be loosely compared to a reading on a blood Glucose meter whish is instant here and now (and in different units) or a reading on a CGM which is of glucose in interstitial fluid rather than the blood and so is delayed about 15 min compared with the blood.
 
Thank you, and thank you! I was trying to get my head around how the average of lots of readings of 8 or 9 could be 50, but I understand it's different units now - took me a while!
 
There's not a direct read-across as they measure different things in different ways. I tried a Libre and it wasn't at all accurate in predicting the estimated A1c - and neither was estimating likely A1c going off fingerprick tests. I also didn't find it OK being told by the Libre that 10mmol/l was "acceptable". That got changed.

The Libre is really useful in showing you what happens when you're not testing - asleep, driving, exercising, that sort of thing. With both the Libre and fingerprick tests you can make an informed guess as to where your A1c might be - but in my case it was just a (wrong low) guess.
 
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