Or just as likely the meter will give a lower result because the times of testing underrepresent the period of time spent with high BG. It's a **** shoot. The one thing you can be sure of is that the 90 day average BG will never match the HBa1c, (even after "conversion"), except by blind luck.The meter will usually give a slightly higher average than a A1c result as one often will measure when the BG is elevated. An average BG estimated by the meter can never replace a HBA1c test though.
Or just as likely the meter will give a lower result because the times of testing underrepresent the period of time spent with high BG. It's a **** shoot. The one thing you can be sure of is that the 90 day average BG will never match the HBa1c, (even after "conversion"), except by blind luck.
I have only recently started testing again since I started the low carb diet for the past two weeks ,but even when im strict with the diet and moderate exercise I am still getting unexpected high readings 9 or 10 two hours after eating , I do wonder about the accuracy of these meters (microdot)
11.8 about 3 months ago
I'm going to try and talk a strategy with my dietician/nutritionist, though i've already put together a food diary to catalog my eating habits, as my diabetic nurse has urged me to eat in more structured intervals such as breakfast, lunch and dinner since I am used to just eating at random times during the day whenever I feel hungry. As I first told her this I did come to expect her to respond that it's difficult to cover every random time that I eat with insulin, and she knew that my HbA1c reflected on me not injecting for everything that I ate. Last hba1c was unreadable, if I had to guess, i'd say it's between 16% and 20% right now, my goal by october when I have my next test is to get it at least below 16% so it can be read.
I've sort of ran low these past few days on purpose just to see if it might make a difference.
Some interesting discussions about HbA1c and meter readings in some posts in this thread, but there is more to it.
If you use a CGM which takes a sample every 5 minutes, and then upload the data to the software, it will give you the mean and the SD over the period you choose. The same applies to a "spot" BG meter (although, as stated, some will also display on the meter the 7-day, 14-day, 30-day, and 90-day means, and the number of samples).
To sample a repetitive waveform (such as sinewave or fixed-ratio square-wave etc), you should sample at twice the frequency at fixed intervals. But if the waveform is quasi-random or random, then the sampling interval can also be random, but with a rate that should be double the rate from maximum to minimum. So if you have one large swing per day, you do not need to catch that large swing, you only need to sample at a higher rate than the largest swings.
To prove my point, from personal experience, for several years my HbA1c was between 6.5% and 7.1% (taken at typically 6-monthly intervals). But, on my meter, my average was 11 mmol/l with an SD of 5 !!!!
My specialist said that the HbA1c was the more reliable of the two, but the closer I questioned this, with more and more examples (at each consultation) of waveform sampling, the more I became convinced that the meter was telling the truth. As a result, a "blind" CGM was used on me for 6 days, which gave an average of 10.5 and an SD of 5 !!!
So why was the HbA1c so wildly wrong ?
The answer is that the HbA1c test is not always correct, it depends on many factors. Anemia is one factor (not the only one) that makes HbA1c read low, and BG read high. There is another test called Fruxtosamine, which I had, and guess what, it came out at an equivalent HbA1c of 9% (Fructosamine is not the same at all, and it only measures the average over 3 weeks, but there is a table for equivalence).
Thus, if there is a wide discrepancy between HbA1c and average BG on your meter, there is reason to doubt the HbA1c, providing that you are "sampling" frequently enough over the same 90-day period. Note that, typically, average BG should be about 1 (no more than 2) mmol/l higher than the percent of the hbA1c
e.g. average BG of 7.5 and HbA1c of 6% is fine, average BG of 9 and HbA1c of 6% is questionable (provided there is sufficient sampling on the meter, my typical sample-rate is 500 times in 90 days)
Today I got my hba1c results (my 3rd since diagnosed in April 2015) and im really happy. In April my hba1c was 98 and as of September 17 I was 44.
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