Caffeine Ingestion to Counter the Exercise-mediated Fall in Glycaemia in Type 1 Diabetes

Inclusion Criteria: * Type 1 diabetes for ≥1 year and negative C-peptide (\<100pmol/l) * Male and female aged 18-45 years old * HbA1c \<8.5% (69 mmol/mol) based on analysis from the central laboratory unit of Bern University Hospital * Using multiple daily injections * Using insulin degludec (Tresiba; Novo Nordisk A/S, Bagsværd, Denmark) as basal insulin for a minimum of 3 months * Written informed consent * Able and willing to adhere to safe contraception during the study and for 2 weeks after completion of the study. Safe contraception comprises double barrier methods (hormonal contraception \[like: oral contraceptive pills or intrauterine contraceptive devices\] together with a mechanical barrier \[like: condom, diaphragm\]). Exclusion Criteria: * Physical or psychological disease likely to interfere with the normal conduct of the study as judged by the investigator * Continuous subcutaneous insulin infusion (using an insulin pump) * Hypoglycaemic unawareness (Gold likert score ≥4) or having experienced any episode of a severe hypoglycaemic event within the last 6 months (i.e. need of third-party assistance). * Current treatment with drugs known to interfere with metabolism e.g. systemic corticosteroids, SGLT2 inhibitors, Glucagon like 1 peptide- receptor agonists, or metformin. * Relevant diabetic complications as judged by the investigator and based on medical record check (no cardiovascular disease and no significant microvascular disease) * Microalbuminuria (as defi…