Aims: Implementing exercise programs in individuals with type 1 diabetes (T1D) may precipitate glycaemic fluctuations. A better understanding of these fluctuations is essential for developing appropriate glucose management strategies. We aimed to assess glycaemic excursions and their progression during a 2-month training program, comparing fluctuations around exercise sessions with those of non-exercising days. Methods: Nineteen (13 female) adults with T1D participated in 2-3 supervised 90-minute combined (aerobic/strength) exercise sessions per week, over 2 months. Glycaemic excursions (continuous glucose monitoring) were measured during specific periods (24-hour, nocturnal; periods before, during, after exercise sessions) and compared between exercise and non-exercise days (linear mixed models, logistic regressions). Results: Nights following exercise sessions showed a reduced risk of hyperglycaemia (>10.0 mmol⋅L⁻¹) vs. non-exercise nights. This difference diminished over the weeks of training, alongside a progressive increase in the risk of time >16.7 mmol⋅L⁻¹ during the early and late recovery phases of exercise. Overall, regardless of exercise session occurrence, level 1 and 2 nocturnal hypoglycaemic risk increased as the training program progressed. Conclusions: Initially, acute exercise sessions reduced nocturnal hyperglycaemia without increasing hypoglycaemia. However, over time, the risk of nocturnal hypoglycaemia increased, highlighting the need for vigilant glycaemic supervision, particularly at night, even on non-exercise days.