- The goal of insulin therapy in type 1 diabetes (T1D) is to reduce hemoglobin A1C (A1C) to ≤7.0% (53 mmol/mol) with minimal hypoglycemia. We investigated the possibility that "insulin timing" would improve A1C without incurring severe hypoglycemia in volunteers with T1D over a 6-month observation period.Forty healthy adult volunteers with T1D were randomly assigned for 6 months to either a control group or an insulin timing group. The primary endpoint was the difference in A1C between the two groups. As a secondary endpoint, both groups were further divided to assess the importance of the baseline A1C in determining the response to timing. The insulin timing algorithm altered the time when the meal dose of insulin was injected or infused from 30 minutes before the meal to 15 minutes after the meal, depending upon the premeal blood glucose concentration.An improvement in mean A1C was observed in the timing group compared with no change in the control group, but this improvement did not reach statistical significance (P>.05). In contrast, when the two groups were analyzed according to baseline A1C, the timing volunteers with baseline A1C values in the upper half (separated by the A1C median of 7.45% [57.9 mmol/mol]) of the timing group had a more robust response to timing (decline in A1C) than the upper half of the control group (P<.05).Insulin timing is a patient-centered translational approach that is safe and effective in improving A1C in individuals with T1D with an elevated A1C.A1C = hemoglobin A1C ANOVA = analysis of variance CGM = continuous glucose monitoring CSII = continuous subcutaneous insulin infusion MDI = multiple daily injection T1D = type 1 diabetes.