HbA1c is a measure of your average blood glucose value, typically over the past 3 months. An HbA1c value of 5.6 or below is considered normal. A value between 5.7 to 6.4 suggests that you may be pre-diabetic and 6.5 and higher is considered diabetic. While HbA1c is an adequate “rule of thumb” type of measure, it does not tell you how much your glucose levels vary during any given period or in response to stimuli such as food, exercise, sleep and stress. This variability is referred to as glycemic variability (GV). The higher your GV, the more of a problem it is and the more damage it causes your heart.
Available data indicates that nearly 19% and 25% of people with a “normal” HbA1c level (< 5.6) become pre-diabetic and diabetic respectively, over time. A CGM allows us to identify GV fluctuations now, and to help at-risk individuals avoid diabetes altogether or to reverse the condition, if they already have it.
This American Diabetes Associations article discusses the subject at greater length:
This paper studies the incidence of diabetes and prediabetes, as well as the predictors of progression from normal glucose tolerance to various stages of dysglycemia, pre-diabetes and diabetes, in the Asian Indian population in the US.