That's not really accurate. HbA1c is essentially an integrator of blood glucose over time. But it doesn't tell you anything about instantaneous blood glucose which is what CGM users typically want to know. The non-diabetic CGM users are generally trying to fine tune their diets by measuring their response to different foods or feeding times (they're seldom fasting for extended periods). And there is a significant genetic variance in the hemoglobin turnover period which skews HbA1c results for some patients.
Both assays have value but they're really for different purposes
> fine tune their diets by measuring their response to different foods or feeding times
Needing to get such feedback from diet is completely unnecessary. It is very easy to estimate the rise in glucose using these factors: percentage of fiber, how processed the food is, how it was cooked (high-heat (bad) vs low-heat (good)), whether the carbs are complex carbs (fibrous) or simple carbs (starch), and whether the meat is red or white.
> variance in the hemoglobin turnover period
Whether there is variation or not, it is still the thing to optimize. Your point is like saying there is significant turnover of how people spend money, so they don't have to bother looking at their bank balance. Also, I hope you're not claiming that the reference range is vastly different for certain people.
Unless one is diabetic or an athlete, given basic nutritional knowledge, there is no benefit to a CGM over HbA1c.
It's not about reference range. There are significant individual variances in postprandial blood glucose response to specific foods based on genetics, gut microbiome, time of day, recent activity level, etc. Empirically it seems that serious endurance athletes have been able to gain a performance advantage by using a CGM to optimize their diets.
The benefits for other people are questionable. But if a CGM gets them to be more mindful of what they're ingesting then that seems like a positive.
That's fine, but it can be misleading at times. For example, metabolic damage to fasting glucose from red meat and high-AGE foods can develop over time, and it won't show immediate results via the CGM. Not all things that cause diabetes show an immediate rise in blood glucose, only some do.
Both assays have value but they're really for different purposes