This study evaluates the impact of menstrual cycle phases on insulin sensitivity, glycaemic control, and insulin requirements in women with type 1 diabetes (T1D). It aims to quantify differences between the follicular and luteal phases using data from the Tidepool Data Platform. Key endpoints include modelled insulin sensitivity, mean glucose, Time in Range (TIR), and total insulin dose.

Secondary objectives include assessing phase-specific variability in the endpoints and differences between participants.

The study follows a decentralized, anonymized data collection approach, with participants using continuous glucose monitors (CGMs) and insulin pumps or smart pens. Glycaemic outcomes and insulin requirements will be compared across menstrual cycle phases using linear mixed-effects models to account for repeated measures within individuals. Cycle phase-specific variation in insulin sensitivity will be quantified using a hierarchical Bayesian state-space model, which estimates a latent insulin sensitivity parameter from CGM time series data while accounting for measurement noise and temporal dynamics.

The findings are expected to improve understanding of glycaemic dynamics across the menstrual cycle and inform future diabetes management strategies.

Inclusion criteria

People are eligible to participate in the study if they:

• are living with T1D;
• are willing to upload diabetes-related data to the Tidepool Data Platform;
• are using a continuous glucose monitoring (CGM) system;
• are using an insulin pump or a smart pen for most of their insulin delivery;
• are willing to track and share their menstrual cycle data;
• are 18 years old or older;
• give consent to share their anonymized data for research.

This study includes adults (18+) living with type 1 diabetes (T1D) who use a continuous glucose monitoring (CGM) system and either an insulin pump or a smart pen for insulin delivery. Participants must be willing to upload diabetes-related data to the Tidepool Data Platform, track and share their menstrual cycle data, and provide consent for their anonymized data to be used in research.