Even though the long-term variability of glucose homeostasis has emerged as a risk factor for adverse outcomes in diabetes, there exists no universal consensus on its definition and assessment, but the determination of quarterly HbA1c fluctuations would be an appropriate metric. From the analysis of retrospective studies conducted in persons with type 2 diabetes, the risk for adverse outcomes appears to become significantly increased when the coefficient of variation for HbA1c (%CV for HbA1c) is above 5.0%. However, should the number of HbA1c readings be greater than four for completing a clinically relevant assessment, the follow-up period would be longer than one year. Such a delay is not clinically acceptable for rapid clinical decisions. To conciliate the scientific relevance and practical approaches with minimal number of HbA1c measurements, we assessed the HbA1c variability from two successive HbA1c readings. For perspective in care the 5.0% threshold of the %CV for HbA1c was converted into lower and upper limits of visit-to-visit differences in absolute HbA1c levels. These HbA1c dependent limits (± 0.X% i.e., [X/10]% for an HbA1c level of X%) easily permit to decipher HbA1c stability and lability in diabetes across the spectrum of HbA1c levels and further to adjust the treatment.