A Research Study to See How Insulin Icodec Helps People With Type 1 Diabetes Control Their Blood Sugar

Inclusion Criteria: * Signed consent obtained before any study-related activities (study-related activities are any procedures related to recording of data according to the protocol). * The decision to initiate treatment with commercially available insulin icodec has been made by the participant/legally acceptable representative (LAR) and the treating physician before and independently from the decision to include the participant in this study. * Male or female, age greater than or equal to (≥) 18 years at the time of signing informed consent. * Diagnosed with T1D ≥ 1 year before signing informed consent. * Treated with multiple daily insulin injections (daily basal insulin analogue and bolus insulin analogue regimen) ≥ 6 months before signing informed consent. * Available HbA1c value less than or equal to (≤) 90 days prior to the 'Initiation visit' (V1) or HbA1c measurement taken in relation with the 'Initiation visit' (V1) if in line with local clinical practice. * Treatment naïve to once-weekly insulin prior to the 'Initiation Visit' (V1). Exclusion Criteria: * Previous participation in this study. Participation is defined as having given informed consent in this study. * Treatment with any investigational drug within 30 days prior to enrolment into the study. * Mental incapacity, unwillingness or language barriers precluding adequate understanding or cooperation.