Changes in Basal and Bolus Insulin Requirements with Tirzepatide as an Adjunctive Therapy in Adults with Type 1 Diabetes Using Tandem Control-IQ

Abstract

Introduction: This study was aimed at investigating changes in insulin requirements and glycemic outcomes in adults with type 1 diabetes (T1D) using Control IQ (Tandem Diabetes) automated insulin delivery system (AID) over 8 months of tirzepatide treatment.

Methods: In this single-center, observational study, we collected demographic, A1c, weight, sensor glucose, and insulin dose data for adults with T1D who were using AID and initiated tirzepatide adjunct therapy for clinical indications (n = 11, median age 37, 64% female and mean body mass index of 39.6 kg/m²). Data were compared from baseline and over 8 months.

Results: Within 2 months of tirzepatide treatment, there were significant reductions in total daily insulin [median (IQR) 73.9 (47.6-95.8) to 51.7 (46.7-66.8) units/day, p < 0.001], basal insulin [47 (28.2-51.8) to 32.4 (25.5-46.3) units/day, p < 0.001], and bolus insulin [31.4 (19.9-38.3) to 17.9 (14.9-22.2) units/day, p < 0.001] requirements. Insulin dose reduction from 2 to 8 months was modest. The frequency of user-initiated boluses did not differ throughout the study. Despite reductions in total insulin requirement, time in range (70-180 mg/dl) increased by 7%, A1c reduced by 0.5%, weight reduced by 9%, without increase in time below 70 mg/dl.

Conclusions: This pilot study provides clinical guidance on insulin titration for adults with T1D who may initiate tirzepatide therapy. Based on the findings of this study, we recommend reducing 25% of total daily insulin dose at tirzepatide initiation in adults with T1D using AID with baseline A1c of less than 7.5%. Higher doses of tirzepatide were associated with greater weight loss, however, the reduction in insulin requirement was minimal.

Keywords: Automated insulin delivery; HbA1c; Obesity; Tandem control IQ; Time in range; Tirzepatide; Type 1 diabetes; Weight loss.

Fig. 1

Delivered daily insulin doses and bolus counts at baseline, 0–2, 2–3, 3–6, 6–8 months. All timepoints were compared to baseline. *p < 0.05, **p < 0.01, ***p < 0.001. Of 11 participants, two were on 2.5 mg tirzepatide, four were on 5.0 mg tirzepatide, and five were on 7.5 mg tirzepatide at 3 months. At 6 months, two were on 5.0 mg tirzepatide, three were on 7.5 mg, three were on 10.0 mg, one was on 12.5 mg, and two were on 15.0 mg tirzepatide. At 8 months, two, one, three, three, and two patients were on 5.0, 7.5, 10.0, 12.5, and 15.0 mg tirzepatide, respectively

Fig. 2

Percent dose reduction for median total daily insulin (blue solid line), basal insulin (orange line), bolus insulin (green line) after tirzepatide treatment at 0–2, 2–3, 3–6, and 6–8-month time intervals

Fig. 3

Time in range (70–180 mg/dl) (green) and time below range (< 70 mg/dl) (red) at baseline, 0–2, 2–3, 3–6, 6–8 months. All timepoints were compared to baseline. Median and quartile values are shown with boxes. One person is missing at the last two timepoints. *p < 0.05, **p < 0.01, ***p < 0.001

Fig. 4

Ambulatory glucose profiles at the baseline (dark blue solid line) and after tirzepatide treatment (post-baseline) (orange solid line). a 24-h glucose course. b Glucose course following user-initiated boluses via carbohydrate entry to the pump