Hi Everyone
Had results back from diabetes 3 month review for type 2 at 56 mmol/mol Doctor says Satisfactory
Have been using Glucose monitor for 3 Months average has been 7.5mol = 47mmol/mol
Testing 2hours after meals in the Morning generally twice a week
Question is the Hba1c accurate
Are Glucose Monitors Accurate
and should I self test at different times of the day before breakfast and before going to bed
Any advice
Hi
The problem is you can't really average your fingerprick readings and predict your HbA1c. They test different things, in different ways. I think a reading twice a week or so isn't going to give you much useful information.
Fingerprick readings test the blood glucose level there and then as a snapshot. There is an acceptable 15% inaccuracy for these, 95% of the time. In practice that means that a true BG value of 10mmol/l could show as anything between 8.5mmol/l and 11.5 mmol/l. One in 20 readings could be outside this range. The issue with this is that if you only do one test you don't know whether your BG is on the way up, or the way down, or whatever. You also don't know what it's doing when you're not testing. Bit like driving and only checking the speedo every hour or so.
The other thing is that averaging your testing can be very misleading. 4 tests all at 8.0 - average 8.0. 4 tests 5.0, 5.0, 11.0, 11.0, also average 8.0. The variation and the high and low points are (in my opinion) much more informative than a mean.
This is why many of us on here don't random test but instead recommend a test pattern that takes a baseline reading immediately before food, and then another two hours later. The intention is to be within 2 mmol/l of the baseline, and not above 8.5mmol/l. This is not to see "how high you go" (the peak will often be somewhere in the first hour). This testing pattern allows us to have an idea of how well our system dealt with the carb/glucose in what we ate. If your system can return you to close to baseline after two hours, that meal is probably OK for you at present, and won't raise your BG unacceptably. If not, there's too much carb/glucose in it for you to handle right now.
Personally I only test around food, and don't do that all that much these days unless it's something new. I found morning and evening readings not much help, because there's not much you can do about the morning reading, which is largely set by what your liver does in adjusting glucose levels. I just can't see what T2 me can learn from an unstructured late night reading.
HbA1c tests count the number of glycated red blood cells -red blood cells that have had a glucose molecule attached to them - at the point of test. This can be used as a useful proxy for blood glucose levels over the last 3-4 months, which is the lifespan of a red blood cell. It's not an average, because it's heavily weighted (around 60%) towards the last month.
HbA1c tests are supposed to have an acceptable inaccuracy of no more than 5%, 95% of the time. A true value of 50mmol/mol could therefore be shown as anywhere between 47.5 or 52.5 mmol/mol. This is why if you have an HbA1c around 50 at the point of diagnosis, they will invariably do a second test. There are some issues with the HbA1c test (eg for people with anaemia) but they are well known, and it's generally OK as a longer term indication of your overall blood glucose level.
I just want to underline that regular, structured, and recorded testing, in my opinion, is the key thing to taking control of your blood glucose level and reducing it (if you want to). For me that, plus a very low carb lifestyle informed by testing, turned my T2 condition around within a couple of months. I've not had an HbA1c test result at diabetic level since January 2020.
