Hormonal variation during the menstrual cycle can influence glucose levels in women with type 1 diabetes. A study published in Diabetology found that hybrid closed-loop insulin delivery maintained stable glucose control across all cycle phases, achieving nearly 70% time in range.

The prospective study included 15 premenopausal women with a mean age of 38 years, average HbA1c of 7.12%, and diabetes duration of 21 years. Participants were followed for three consecutive menstrual cycles, divided into menstrual, luteal, and rest phases.

Mean glucose was higher during the luteal phase (p = 0.029 vs menstrual; p = 0.018 vs rest of cycle). The average time in range (TIR) decreased in the luteal phase (p = 0.015 vs rest of cycle), while insulin requirements rose (p = 0.017). Time below range (TBR) increased during menstruation (p = 0.007 vs luteal phase). Despite these variations, the overall TIR remained close to 70% in all phases, indicating stable glucose regulation.

These findings show that hybrid closed-loop insulin delivery can mitigate cycle-related glucose variability, supporting consistent glycemic stability in women with type 1 diabetes.