Newbie- Is there a relationship between HbA1c and finger prick metre test?

[Jenny105]

Out of interest is there any relationship between the HbA1c test and the finger prick metre test. eg my first blood test was mmol 96. The first finger prick test 18.6 a week later. (5x )
It looks as if the my target is 58mmol. My own tests average 7.9 over 10 days, spasmodic testing. From the latter the readings have gone down. But is there a correlation between the 2 readings. 7.9 v 58mmol target . Thanks

 

[helli]

Hba1c is an indication of your average blood sugar levels (measured via finger pricks) at all times over 3 months.
Confusingly, they are in different units.
Unfortunately, finger pricks only give us the reading at the time we take it no give no indication of highs or lows since the last test so trying to estimate your HBA1c for a few finger pricks is going to be very inaccurate. Some phone apps attempt to make an estimate but I think this is very misleading.
CGMs are better at estimating because they take readings every 5 minutes but they are still not accurate.

 

[Jenny105]

@helli Hmmmm so the blood test taken by doc, doesn't bear a relationship to the daily metre tests. I thought there wasn't but it would be nice to keep a rough track of progress.
I guess I can say the the finger readings have gone down by approx 2/3rds in 6 weeks. 1/3 in the first 3 weeks and 1/3 again in 2nd 3 weeks. 😎
I wish my weight would stop going down !!! At least it's not dropping by a 1/3 😉 and is still within BMI safe range.

 

[Docb]

What seems to be the case is that you can relate your average finger prick test to HbA1c, there are various charts on the interweb if you go looking. The average would need to be from a reasonable number of tests taken at all times of day.

My last 60 day average is for example 5.7 and I found somewhere that this should equate to an HbA1c of 40. Had a result a couple of weeks ago of 38, which as far as I am concerned is a match.

 

[Jenny105]

That sounds good. It must be nice to know you are winning. And that its possible to chase your progress yourself
.My nurse asked for 1 test a day at a variety of times. I have done more than that. I could work out the average of all of those over say 6 weeks. Or wait a while until the recent lowering can be averaged out. Thanks

 

[helli]

If your average finger prick reading is going down, so will your Hba1c.
But by how much is very much a huge estimate as you do not know what is happening between finger pricks.

 

[Jenny105]

I know some shoot up still after certain meals, others dont rise much . Im not sure how the Nurse is using the figures that Ive given her - the once a day ones. Shes not very communicative.🙄

 

[JJay]

This might help

"Rainbow" Chart

 

[Jenny105]

Thats just the thing. On the whole I'm green to yellow. My target is 58 . That gives me a rough idea.
Next bevy of blood tests in early Nov .

 

[Drummer]

From the numbers I see after eating, my Hba1c would be in the 30s according to the charts and other information - but it isn't.
The charts were made by keeping tabs on blood glucose and then taking the Hba1c of the individual being scrutinised, but non standard recycling of red blood corpuscles can cause variance, so I go with that.

 

[Burylancs]

Out of interest is there any relationship between the HbA1c test and the finger prick metre test. eg my first blood test was mmol 96. The first finger prick test 18.6 a week later. (5x )
It looks as if the my target is 58mmol. My own tests average 7.9 over 10 days, spasmodic testing. From the latter the readings have gone down. But is there a correlation between the 2 readings. 7.9 v 58mmol target . Thanks

They measure two different things. There is a formula that collates them JFGI. HbA1c is not an average of your own blood tests. Upto 2012 HbA1cs were measured on %s, as they still are in many parts of the world e.g. 48 is 6.5% in USA. We adopted European Protocols, perhaps we will return to British %s with Brexit. The HbA1c does measure the amount of glucose stuck to blood cells over 3 months but it is skewed to the last ten days. There is a merry dance of glucose that was stuck to blood cells becoming unstuck and cells free of glucose three months ago getting stuck with it. The traditional routine for T2s is to be abstemious and very good in the ten days upto the HbA1c test and then celebrate with a Mars Bar on your way home ;-)

 

[Jenny105]

My great grandma came from Bury area.
Thanks for the detail. Sounds wicked. My condition came on very quickly (I have blood tests for other things 3 -4 times a year, my Doc is amazed at the sudden onslaught - 96 .)
Can one divest oneself of these sticky cells. ? Diet ? Tablets? Insulin ? if needed
A friend I've known for 50 yrs had diabetes 20yrs ago. Managed to ( control) it 6 yrs ago - stopped tablets y 10rs ago. Last week she had a massive stroke. Cause not known as yet. - a salutary warning. 🙄

 

[Burylancs]

My great grandma came from Bury area.
Thanks for the detail. Sounds wicked. My condition came on very quickly (I have blood tests for other things 3 -4 times a year, my Doc is amazed at the sudden onslaught - 96 .)
Can one divest oneself of these sticky cells. ? Diet ? Tablets? Insulin ? if needed
A friend I've known for 50 yrs had diabetes 20yrs ago. Managed to ( control) it 6 yrs ago - stopped tablets y 10rs ago. Last week she had a massive stroke. Cause not known as yet. - a salutary warning. 🙄

Well what you do is get control of your bgs by diet, exercise, medication etc so there is less glucose in your bloodstream to get stuck to new blood cells.

 

[LilLady]

Out of interest is there any relationship between the HbA1c test and the finger prick metre test. eg my first blood test was mmol 96. The first finger prick test 18.6 a week later. (5x )
It looks as if the my target is 58mmol. My own tests average 7.9 over 10 days, spasmodic testing. From the latter the readings have gone down. But is there a correlation between the 2 readings. 7.9 v 58mmol target . Thanks

This could literally be my question Jenny.
I am so confused. I found this chart online but unsure of accuracy, my HBAC1 was 139 or 119 lost my slip, but my BG's were never checked at this appt, so I haven't a clue how high they were?
They're now on average 6's 7's 8's. Would love to know what this actually equates to.
My 3 month review and HBAC1 was delayed due to the national blood bottle shortage.

 

[Docb]

@LilLady, as somebody has said elsewhere you are getting a bit hung up on your readings. All too easy to do and is the "official" reason why meters are not prescribed routinely for T2 diabetics.

If your readings are mostly 6's, 7's and 8's with the odd excursion up to 9, then your average will be around 7 and this will correspond to a HbA1c around 40. Might be a bit higher or a bit lower, the precision in the prediction is poor. One thing you can be sure about is that it will be a long, long way from your starting point of 139 and that is an amazing change and says that what ever you are doing is working very well.

Keep your spot readings in the range 5 to 10 by spotting and avoiding foods that push you into double figures and I am sure you will be pleasantly surprised by your next HbA1c result.

 

[Jenny105]

@LilLady . Im using JJays rainbow chart as a rough guide. Like you Ive come down from around 100 HbA1c to readings of 5 - 9 (not taken all the day long). My HbA1c came out of the blue , regular bloold tests across the board have never shown anything...... my only thought in back of my mind is the vaccination taken in Frb and May. I know 2 other people who have issues since then -out of the blue. All weighing less than 9 1/2 st (130Kg)? Good diets , maybe lockdown abberations

 

[Docb]

So as not to give anybody a fright.... 9 1/2 stone is 60kg!

 

[helli]

Please please bear in mind that JJay's Rainbow chart shows the average blood sugar readings at all times. This can be very different from the average of the 4 or 5 finger pricks that you take in a day. For most people the average 24/7 is higher than the average of your finger pricks because it is rare to prick at the peak.

I write this because I have often seen people disappointed by their HbA1C based on what these charts suggest they should be.

A CGM is taking readings every 5 minutes but they can be out with regard to their HbA1C calculation - my Libre estimates about 10 less than my blood test results for HbA1c.

My approach is to look for trends. If my finger pricks are coming down, I expect my HbA1C to come down but I do not use the rainbow chart to work out how much it will come down as I do not have sufficient data.

 

[ColinUK]

If you log enough readings in the mysugr app then it’ll estimate HbA1C and the estimate isn’t a million miles away from the likely test results.

 

[Eddy Edson]

Not meaning to muddy waters further, but if you're going to focus closely on BG and HbA1c you have to bear in mind that the relationship isn't exact. It's an empirical, statistical relationship.

The researchers responsible for it took a bunch of CGM readings from a bunch of non-diabetics and used them to calculate average BG levels; then compared these averages to HbA1c results for the same people; and came up with a best-fit formula. Individuals can vary widely from this best fit, with most of the variability due to individual differences in average red blood cell life.

The Wikipedia entry helpfully includes the results of this original study, below (in both UK-style and other country-style units). https://en.wikipedia.org/wiki/Glycated_hemoglobin

People like to say eg that an HbA1c of 42 mmol/mol "corresponds" to an average BG level of 7.0 mmol/L. But that's just the "best fit" value. 7.0 mmol/L is the value for the "median person", but other people can be a lot higher or lower than that. As shown in the table, it wouldn't be amazing to find that you get an HbA1c of 42 even though yr average BG is as low as 5.5 mmol/L or as high as 8.5 mmol/L.

Really, it's best to think of HbA1c as a pretty squidgy kind of metric. Very high = need to do something; less high = less urgency; big changes probably mean something big has happened with your bod. Pushing things further than that might be trying to squeeze a bit too much meaning out of it.

%	mmol/mol[37]	mmol/L	mg/dL
HbA1c	eAG
5	31	5.4 (4.2–6.7)	97 (76–120)
6	42	7.0 (5.5–8.5)	126 (100–152)
7	53	8.6 (6.8–10.3)	154 (123–185)
8	64	10.2 (8.1–12.1)	183 (147–217)
9	75	11.8 (9.4–13.9)	212 (170–249)
10	86	13.4 (10.7–15.7)	240 (193–282)
11	97	14.9 (12.0–17.5)	269 (217–314)
12	108	16.5 (13.3–19.3)	298 (240–347)
13	119	18.1 (15–21)	326 (260–380)
14	130	19.7 (16–23)	355 (290–410)
15	140	21.3 (17–25)	384 (310–440)
16	151	22.9 (19–26)	413 (330–480)
17	162	24.5 (20–28)	441 (460–510)
18	173	26.1 (21–30)	470 (380–540)
19	184	27.7 (23–32)	499 (410–570)