HbA1c not aligning with home testing?

Glink

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252
Type of diabetes
Prediabetes
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I'm going to try to rephrase this for clarity (original post below) to see if that gets any responses.

My situation is: I've had fairly steadily rising FBG readings on my home metre, and random-seeming highs throughout the day (I can feel them; get shaky and then test at 7.7-11 several hours after eating anything). But, I get quarterly blood tests and my HbA1c is still great (always 5.3-5.6). My home metre seems calibrated with the FBG drawn at the lab, so I don't think it's off. I thought for sure this recent HbA1c would reflect what feels like a turn for the worse and I could discuss what to do about it with my doctor, but with only my home readings to go on I doubt he'll see anything to discuss.

My questions are: Has anyone else experienced this kid of thing? What are the possible explanations for HbA1C being good while other numbers are looking more and more diabetic?
Thanks!

--
Old, rambly post:

I get quarterly blood tests, and test most days at least once on my home metre. I try to control my sugars using a LCHF diet and metformin. When my sugars are high, I fast until they get lower again.

When I was first diagnosed, 2 yrs ago, a LCHF diet alone was enough to bring both my FBG and postprandial readings to normal.
Then it took metformin, then more metformin.
Now I cannot get FBG normal anymore on matter what. With my current dose of metformin plus strict LCHF I can keep it in the prediabetic range (if I eat a "normal" supper I have diabetic level FBG), and can usually keep my postprandials good, but I've been having more and more high readings, like several hours after lunch still 7.7.

But here's the puzzler: my HbA1c is good! (5.3-5.6 range) Why? I don't ever catch hypos, so I don't think it's reactive hypoglycaemia.

I've been having symptoms (like that crushing fatigue, ugh, swelling feet, frequency at night) again, along with my higher trend of FBG readings, but the great HbA1c means my doctor thinks everything is A-Ok. What could be going on here?
 
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GrantGam

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2,603
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I'm going to try to rephrase this for clarity (original post below) to see if that gets any responses.

My situation is: I've had fairly steadily rising FBG readings on my home metre, and random-seeming highs throughout the day (I can feel them; get shaky and then test at 7.7-11 several hours after eating anything). But, I get quarterly blood tests and my HbA1c is still great (always 5.3-5.6). My home metre seems calibrated with the FBG drawn at the lab, so I don't think it's off. I thought for sure this recent HbA1c would reflect what feels like a turn for the worse and I could discuss what to do about it with my doctor, but with only my home readings to go on I doubt he'll see anything to discuss.

My questions are: Has anyone else experienced this kid of thing? What are the possible explanations for HbA1C being good while other numbers are looking more and more diabetic?
Thanks!

--
Old, rambly post:

I get quarterly blood tests, and test most days at least once on my home metre. I try to control my sugars using a LCHF diet and metformin. When my sugars are high, I fast until they get lower again.

When I was first diagnosed, 2 yrs ago, a LCHF diet alone was enough to bring both my FBG and postprandial readings to normal.
Then it took metformin, then more metformin.
Now I cannot get FBG normal anymore on matter what. With my current dose of metformin plus strict LCHF I can keep it in the prediabetic range (if I eat a "normal" supper I have diabetic level FBG), and can usually keep my postprandials good, but I've been having more and more high readings, like several hours after lunch still 7.7.

But here's the puzzler: my HbA1c is good! (5.3-5.6 range) Why? I don't ever catch hypos, so I don't think it's reactive hypoglycaemia.

I've been having symptoms (like that crushing fatigue, ugh, swelling feet, frequency at night) again, along with my higher trend of FBG readings, but the great HbA1c means my doctor thinks everything is A-Ok. What could be going on here?
I'd go with the lab tests over any home meter.

What meter are you using? Some are regularly reported to read out higher than you actually are. The SD Codefree is an example of one which you'll hear about from time to time on here.

Have you tried another meter?
 

Bluetit1802

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I do not agree with @GrantGam . I would go with your meter. It is well known that the Hba1c test is not accurate if you have any sort of red blood cell abnormalities, including things like iron deficiecy, anaemia and so on. It is also inaccurate for those of us whose red blood cells do not live the average 120 days. Some people have a quicker turnover of RBC and for them an HbA1c will be lower than finger prick meter tests or continuous glucose meters.

I am the opposite. My HbA1c is always SIGNIFICANTLY higher than both my finger pricking and Libre continuous sensor indicate, even allowing for them possibly reading low. I assume my RBC are long living.

You could ask for an OGTT and/or a Fructosomine test. Your GP may agree if you show him evidence of the discrepancies.
 

Pinkorchid

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If HbA1c tests are not accurate why do they bother to do them... vein drawn blood is supposed to be more accurate than finger prick blood
 
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Bluetit1802

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If HbA1c tests are not accurate why do they do them vein drawn blood is supposed to be more accurate than finger prick blood

That used to be the case, but nowadays most meters are calibrated to convert the capillary whole blood from fingers to plasma blood from veins. Only very old meters will not comply with this. For most people the HbA1c is sufficiently accurate, but we aren't all "most people" As we say all the time, one size does not fit all, and we don't all have average RBC life, even if most do.
 

Glink

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Whenever I get my quarterly lab tests I check the FBG they get against my home metre FBG and it has always been incredibly close (the same if within a short period of time; a little off if there's an hour wait for my blood draw). My fasting glucose as reported by the lab has also been gradually rising. And I have 2 metres that read the same (although both are the same brand).

So in this case I don't think my home metre is "off." I think the HbA1C isn't reflecting what my non-continuous home testing is showing, and I'm wondering why--whether my average could somehow be remaining the same despite these rising numbers when I test, or whether other factors might be making my HbA1c inaccurate. I see many articles online offer vague lists of reasons HbA1c might be inaccurate for some people but I'm not clear what the exact mechanisms/effects are, or which could apply to my situation (lower than expected A1c). Most of what I see about anemia, for example, seems to apply to erroneously *high* A1c rather than surprisingly low readings.
 
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Glink

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I guess if I am still having these problems next time I go see my GP I will see if he'll prescribe an OGTT. Other than that, I guess I just have to wait until there is a clear trend of over-7 FBGs at the lab appointments? I'd rather not, but the only way I seem to be able to avoid it is by not eating and I don't have too much weight I can afford to lose (more than 10 lbs and I'll be "underweight," and I don't have a small frame so I'd rather not go totally skeletal).
 

ringi

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If HbA1c tests are not accurate why do they bother to do them

Firstly they are cheap, with a lab cost of between £2.50 and £3.50 in the UK, they also give a number that does not depend on what someone eats the day before. Before the HbA1c people would "be good" for a few days before having the blood tests....

Then for any given person the trend in HbA1c results seems to be meaningful, for example if the HbA1c is higher then it was a year ago the average BG has been higher over at least a few weeks before the HbA1c test.

But for a small number of people the HbA1c result does not predict what the average BG has been.

Also HbA1c only shows the average BG not highs and lows, and a few people can have BG values that changes a lot, but still have a HbA1c within normal ranges.

At the end of the day, HbA1c results have been shown to be a very good predictor of diabetes complications for people not on medications.
 

Ambersilva

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The meter finger prick test is just an instant snapshot in time. An hour later it will register a different result depending on whether blood sugar is rising or falling. A test taken on one hand can be different to a test taken on the other hand immediately after the first test.

The HbA1c measures the amount of glucose stuck to the blood cells during the previous three months.
 

BeccyB

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Do you tend to test more when you aren't feeling well? This would skew your home results, whereas the HbA1c will be a reflection of your sugars 24/7
 

andcol

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None of this talk about the meters against lab test really answers the OPs question!

My take on it is that you have many times where you are running fairly low (possibly 4s). This compensates for the times when you are high so you get a reasonable average (HbA1c). Of course going to 11 from 4 isnt good (you can feel it) and the fact you do not go over it proves your body still has enough control but not much capacity to push it further.

My suggestion is to squash those peaks into the 8s by reducing your carb intake a little - especiall starchy carbs and sugar.
 

Glink

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Prediabetes
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Yeah, that's the only thing that makes sense if the HbA1C is accurate--that there must be nice low periods I'm just not catching. I do test more when I'm feeling bad, but my FBG is also rising despite pretty consistent LCHF diet for 2 years now. And, I do often also test again a few hours later when I'm feeling better--to make sure I'm better enough to eat (which I consider to be below 6) rather than needing to fast to bring things down more before eating again--and never catch it as low as in the 4's (anymore--2 years ago I used to be able to be in the 4's a lot). Maybe it's happening while I'm sleeping, before dawn phenom hits? I don't know. I feel like it doesn't quite add up, but I suppose without a CGM there's no way to really know.
 

AloeSvea

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I don't really understand the science/physiology stuff behind it, but I have read, consistently, that an LCHF diet does raise your fasting BGs somewhat. Dr Fung says not to worry too much about it, even those of us with blood glucose dysregulation. @Indy51 may have the answer? (She gets my vote as the LCHF go-to-gal and forum expert for such things.)

I find it impossible NOT to worry about Fasting BGs though, as I interpret it as a big sign 'your liver and pancreas are pretty shot, and yr liver is misreading insulin signals, and all those other involved signals, and shooting out blood glucose big time' in relation to food and fat storage. (It's about how insulin signals and glycogen stores work in concert? Or not work well in concert? Isn't it?) But I would be in seventh heaven with a 34-38 HBA1c. In fact, I would not be identifying as a prediabetic anymore! (A super well controlled person with Impaired Glucose Tolerance?)

About that - Um, I'm not sure, if you are on metformin, does one actually know how well one's liver and pancreas are controlling one's BG levels? Do you know how you do without it? for instance. Maybe then your HBA1c would reflect your liver and pancreas not working so well? Because metformin provides your liver with that 'off switch' for spitting out too much blood glucose into an already too high blood glucose situation. Your great HBA1c may be a really good indication of how well metformin works for you, in terms of keeping your BG levels normal on average.
 

Mr_Pot

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As a matter of interest why is the doctor prescribing Metformin when your HbA1c is non diabetic? Also you say you are getting quarterly blood tests but most people who are definitely diabetic don't get them that often.
 

Glink

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I am in Canada so things are a little different from the UK. I am well controlled on lchf and metformin but with IFG and and IGT. And seemingly getting gradually less well controlled--except this impression isn't reflected in the HbA1c test, hence this thread/query.

I got metformin when my IFG kept getting worse despite strict lchf diet & plenty of exercise. We all kind of expect me to turn out to have LADA eventually, hence the vigilence (but they don't do GAD testing in my province, so I'm just sort of left always wondering if/when the other shoe will drop).
 

Glink

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Prediabetes
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Like, I tested a couple hrs after a lchf lunch (leftover steak & cougetti, with some broccoli & a little sugar-less tomato sauce) today and it was 7.9. I used to be able to eat that and not exceed 6.5 2hrs later, but not anymore. Fastings too--used to be in high 4's to low 6's but now rarely below 6.1. Yet, hba1c hasn't really changed. It seems puzzling.
 

Diakat

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Can you get a Libretto in Canada? U.K. Cost is about £50 for two weeks and can be read with most modern smartphones. It would allow you to see trends - I cannot speak for accuracy as I have only used two sensors, one never worked and the replacement often read 3mmol over or under at any point, however I could see stuff I had not before between tests.
 
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Glink

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Prediabetes
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Tablets (oral)
They are supposed to be available here sometime this year, so I will keep my eyes open. I would like to have a better idea of what is going on.
 
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infinitemantra

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Type of diabetes
Type 2
I hva e the same problem. Have been diagnosed as diabetic for just over a year and my H!AC has gone down from 147 to 35 in that time. However my home tests have consistently been considerably worse than my H1AC results. I juts got a control solution to check my meter , but these allow sucgh a range that whilst the meter passed the test there is still room for it to be wrong.

I struggle for a meaningful answer. Home testing meters are allowed to be fairly inaccurate, H1AC may not be a true reflectin of your blood if your blood sugar over time does not last very long. So where are you left when trying to assess your control - for me is getting the number down to 35 success and injust need to maintain? or should I be attempting to get my meter numbers down - currently showing an average of 8.3, against my H1AC equivalent to 6