If they’d used the HA1C test before I was actually diagnosed 20+ years ago they would have discovered I was diabetic. My blood sugar had been high for quite a while but my doctor assumed I wasn’t fasting when he drew the blood in the office for routine tests because I was complaining of feeling sick over a long period of time. They were in the area of 140-160 (acceptable blood sugar was higher back then. They didn’t have pre-diabetes as an official condition and if I remember what he told me was that over 190 was the absolute diagnoses of diabetes.). He thought I’d eaten less than 2 hours before since it was an hour or so after lunch (never asked). I hadn’t and in some cases I hadn’t eaten anything in 14 hours. He finally caught it when it was over 200 and spilling into my urine. When the subject of blood tests comes up I always suggest to people that they tell the doctor when they’ve eaten before they draw blood.
My new doctor at Kaiser views the HA1C as the gold standard and isn’t as concerned about the day to day readings that I take. He still believes in the day to day readings to help you stay on course but as a measure of how your doing he’s going to use the HA1C. The samples are snapshots and don’t measure what’s really going on over a longer period of time. For example the blood sugar could be staying high for longer periods of time and dropping near the time you test or it could be staying near the level you got when you test. His goal for his diabetic patients is to keep their HA1C reading below 7.0 and not have them try to push to keep it within the “normal” range. He feels that there are a number of complications that appear if you reduce the HA1C levels that low consistently.
I think your doctor has it right.