I'm in more or less the same situation as the OP. I've just started testing as I REALLY need to get my HbA1c down. I know that testing doesn't give the same result as a HbA1c test, but by checking fasting sugars and pre and post food numbers I can get a much better idea of what effect the Metformin and diet are having on my BC. Not very scientific I'm sure but it can't do me any harm I guess.
Turns out that if you need practically nothing and take 2000mg of Metformin a day your BC doesn't get too high!!
You’re right the two tests are different. Measuring different things.
Hb1ac is just an average (weighted to more recent weeks at that) of what your bgl has been doing. It can be erroneously affected by things like anemia and red blood cell lifespan. It can comprise of highs and lows (not good) or steady even levels (good). It is a simple check on the overall picture.
Blood glucose levels are a snapshot of right now. In isolation they mean little unless extreme. Well timed and as means of assessing the effect of food and activity along with progress and improvement of overall levels they are every bit as valid and possibly much more useful than hb1ac. It is scientific, not sure why you think it’s not.
I presume you meant eat practically nothing. And if you eat the right things you can eat plenty.
It’s more accurate to say if you eat practically none of the sugary or starchy foods you may not even need the metformin to get good bgl
See the links at the end of my signature for more details.