This study compares insulin icodec, an insulin taken once a week to insulin glargine, an insulin taken once a day. The study medicine will be investigated in participants with type 1 diabetes. The study will look at how well insulin icodec taken weekly controls blood sugar compared to insulin glargine taken daily. The study will last for about 8.5 months.
Diagnosed with type 1 diabetes mellitus greater than or equal to (≥) 1 year before screening.
Treated with multiple daily insulin injections (daily basal insulin analogue and bolus insulin analogue regimen) ≥ 6 months before screening.
HbA1c from 7.0-10.0 percentage (%) (53.0-85.8 millimoles per mole (mmol/mol)), both inclusive, at screening confirmed by central laboratory analysis.
Ability and willingness to adhere to the protocol including performance of self-measured plasma glucose (SMPG) profiles, based on the investigator's judgement.
Known or suspected hypersensitivity to study intervention(s) or related products.
Previous participation in this study. Participation is defined as signed informed consent.
Female who is pregnant, breast-feeding or intends to become pregnant or is of childbearing potential and not using adequate contraceptive method.
Exposure to an investigational medicinal product within 90 days or 5 half-lives of the investigational medicinal product (if known), whichever is longer, before screening.