Continuous exercise may immediately lower glucose levels regardless of Menstrual Cycle Phase, finds study

The study aimed to evaluate the effects of continuous moderate-intensity aerobic exercise (CONT) on glycemic control in women with T1D during different phases of the menstrual cycle. A total of 25 women with T1D were enrolled and completed two separate 30-minute CONT sessions, one during the follicular phase and another during the luteal phase of their menstrual cycles.

Glycemic control was also measured both in the session during exercise with plasma glucose levels and at 24 hours after exercise by continuous glucose monitoring (CGM). The research aimed at determining how the levels of blood glucose varied during exercise and tracked episodes of hypoglycemia and hyperglycemia in the post-exercise hours, based on the menstrual cycle stage.

Key Findings

• The research offered obvious numerical findings concerning the relationship of exercise and menstrual phases in females with T1D:

• At both phases, blood glucose concentration decreased from the baseline value around 155 mg/dL to 110 mg/dL post-30 min CONT, displaying a reliable transient glucose-lowering effect of exercise.

• The frequency of hypoglycemia within the 24 hours after exercise was extremely low, <2%, in both phases of menstruation, and this suggests adequate short-term safety of CONT in this group.

• In contrast, the luteal phase demonstrated an increase in hyperglycemia from 38.2% to 44.2% within the 24 hours after exercise, and this indicates a deteriorating glucose control in this phase.

• In comparison to the follicular phase, increased mean blood glucose levels were noted in the luteal phase after exercise, indicating the effect of hormonal changes on post-exercise glucose control.

• Time-in-range (TIR) was maintained after exercise during the follicular phase but decreased during the luteal phase, supporting the necessity for individualized insulin approaches according to menstrual cycle phases.

This research confirmed that regular moderate-intensity aerobic exercise reduces blood glucose levels right away in women with type 1 diabetes across all menstrual cycle phases. Although glucose stability following exercise is ensured in the follicular phase, hyperglycemia increases and TIR decreases during the luteal phase. These observations indicate that menstrual cycle phases impact exercise-induced glucose control and note the possibility that insulin therapy must be tailored by menstrual phase in order to maximize safety and efficacy in physically active women with T1D.

Reference:

Agustín, R. M.-S., del Pino, A. C., Laguna Sanz, A. J., Rossetti, P., Bondia, J., & Ampudia-Blasco, F. J. (2025). Impact of continuous moderate-intensity aerobic exercise on glycemic control according to different phases of the menstrual cycle in females with type 1 diabetes. Diabetes Research and Clinical Practice, 112192, 112192. https://doi.org/10.1016/j.diabres.2025.112192