The advent of continuous glucose monitoring (CGM) has substantially changed management of type 1 diabetes (T1D). Due to the limitations of HbA1c, CGM devices have been recommended as a central tool for managing patients with T1D. CGM systems provide a comprehensive view of glucose profiles identifying patterns, areas of glucose variability (GV), and times spent in range (TIR), below or above target range, thereby allowing patients to make therapeutic adjustments to improve metabolic control. With the use of CGM, an International Consensus on Time in Range was recently published with the recommendation to spend >70% of time in range (70-180 mg/dL or 3.9- 10 mmol/L) because this level corresponds to an HbA1c level of 7.0% (53 mmol/mol). Despite the limitations of CGM (costs, measurement of glucose in the interstitial fluid, time lag of ~10 minutes), a growing body of evidence supports the use of CGM because it has the potential to improve HbA1c, TIR, GV, and quality of life. Early studies suggest ‘Time in Range’ can effectively predict long-term diabetes complications. Evidence linking high GV and low TIR to diabetes complications is beginning to emerge. HbA1c variability, indicating long-term GV, shows a positive association with micro- and macrovascular complications and mortality independent of the HbA1c level.

In a re-analysis of a landmark study (DCCT), researchers found a strong relationship between different levels of ‘Time in Range’ and diabetes complications: retinopathy and microalbuminuria. As Time in Range increased, complications decreased.

Consistent, in-range blood glucose levels are called ‘flat, narrow, in-range’ (FNIR). This is important to think ‘ideal’ blood sugars: high time in-range and a flat glucose trend line with minimal time above and below range.

Time in tight range (TITR= 70 to 140 mg/dl or 3.9- 7.8 mmol/L) has slowly become popular in diabetes field and could potentially lead to a longer life expectancy as it reduces the risk of complications.