Impact of Meal Insulin Bolus Timing and Bedtime Snacking on Continuous Glucose Monitoring–Derived Glycemic Metrics in Hospitalized Inpatients

<b><i>Objective:</i></b> In hospitalized inpatients, timely administration of prandial insulin with meals is challenging. Furthermore, the glycemic impact of snacking after dinner ("bedtime snacking") without prandial insulin administration has not been previously explored. We present an analysis of the impact of delayed mealtime insulin administration and bedtime snacking on inpatient glycemic control. <b><i>Research Design and Methods:</i></b> We conducted a post hoc analysis from the In-Fi study: a randomized controlled trial comparing Fiasp versus insulin aspart (Novolog) in inpatients with type 2 diabetes. Glycemic outcomes were assessed using the Dexcom G6 PRO continuous glucose monitoring (CGM). We analyzed CGM and insulin administration data from 122 randomized subjects who completed the primary study protocol, which included wearing a CGM for ≥4 meals. This analysis evaluates the impact of delayed mealtime insulin administration and bedtime snacking on glucose control. <b><i>Results:</i></b> Four-hour postprandial time in range (TIR_70-180) was 48% for insulin boluses administered before meals (<i>n</i> = 149) versus 24% when a meal bolus was delayed for >5 min after a meal (mean delay 58.7 min; <i>n</i> = 112; <i>P</i> < 0.001). Bedtime snacking (9 pm-12 am) was associated with significantly higher fasting glucose the next morning (35.2 mg/dL, standard error [SE] = 15.4, <i>P</i> = 0.026) and with a reduced overnight (9 pm-6 am) TIR_70-180 (31.9%, SE = 8.06, <i>P</i> < 0.001), adjusting for bedtime sensor glucose. Bedtime snacking was associated with higher overnight glucose standard deviation (12.3 mg/dL, SE = 3.46, <i>P</i> < 0.001) and with higher overnight glucose percentage coefficient of variation (3.6%; SE = 1.7, <i>P</i> = 0.044), adjusting for initial bedtime sensor glucose. <b><i>Conclusions:</i></b> Delayed mealtime insulin administration and bedtime snacking without insulin administration are significant causes of postprandial and overnight hyperglycemia in hospitalized inpatients. Adjustments in mealtime insulin protocols, attention to food intake, and the potential inpatient adoption of technology, such as CGM and automated insulin delivery systems, are needed to address this shortcoming in inpatient diabetes care.