Prior studies using frequent self-monitored blood glucose in patients with type 2 diabetes on oral medications reported that the relative contribution of fasting glucose gradually increased with increasing HbA1c levels (30% for A1c <7.3% and 70% for A1c >10.2%) . This has led to targeting fasting glucose first to lower A1C in uncontrolled diabetes.

Our study evaluated associations between daytime vs. nighttime mean glucose and time-in-range (TIR; 70-180 mg/dL) with A1C in adults with type 1 diabetes (T1D) (n=340) using Dexcom G6 continuous glucose monitoring (CGM) for at least 6 months. The last 2 weeks of CGM mean glucose and TIR were correlated with four A1C categories (<7%, 7- <8%, 8-<9%, 9-<10%, and >10%) .

With increasing A1C, there was increased mean sensor glucose and reduced TIR for daytime and nighttime (p<0.001 for both) . However, there was no difference in daytime vs. nighttime in TIR (p=0.08) or mean glucose (p=0.42) within four A1C groups. The results were similar when TIR target was changed to 70-140 mg/dL.

Our results suggest influence of mean glucose and TIR on A1C is similar during daytime and nighttime in T1D adults. Thus, either postprandial glucose reduction or fasting glucose reduction strategies should be equivalent in lowering A1C. Our results explain the basis for the benefits of the established use of equal doses of basal and bolus insulin for all A1C levels in these patients.


V. Shah: Advisory Panel; Medscape, Sanofi, Consultant; Dexcom, Inc., Research Support; Dexcom, Inc., Eli Lilly and Company, Insulet Corporation, Novo Nordisk. T. B. Vigers: None. L. Pyle: None. H. K. Akturk: Research Support; Dexcom, Inc., Eli Lilly and Company, REMD Biotherapeutics. D. C. Klonoff: Consultant; AI Health, Dexcom, Inc., Eli Lilly and Company, EOFlow Co., Ltd., Fractyl Health, Inc., Integrity, Lifecare, Inc., Medtronic, Novo Nordisk, Rockley Photonics, Samsung, Thirdwayv Inc., Employee; Diabetes Technology Society.

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