A Research Study to See How Switching From a Daily Basal Insulin to a New Weekly Insulin, Insulin Icodec, Helps in Reducing the Blood Sugar Compared to Daily Insulin Glargine in Adults With Type 2 Diabetes

Prior treatment

• Any episodes of diabetic ketoacidosis within 90 days prior to the day of screening.
• Myocardial infarction, stroke, hospitalisation for unstable angina pectoris or transient ischaemic attack within 180 days prior to the day of screening.
• Uncontrolled and potentially unstable diabetic retinopathy or maculopathy. Verified by a fundus examination performed within the past 90 days prior to screening or in the period between screening and randomisation. Pharmacological pupil-dilation is a requirement unless using a digital fundus photography camera specified for non-dilated examination.

Other illness

• Chronic heart failure classified as being in New York Heart Association Class IV at screening.

Lab values

• Anticipated initiation or change in concomitant medications (for more than 14 consecutive days) known to affect weight or glucose metabolism (e.g., treatment with orlistat, thyroid hormones, or corticosteroids).

• Diagnosed with T2D greater than equal to (≥) 180 days prior to the day of screening.
• HbA1c from 7.0-10.0% (53.0-85.8 mmol/mol), both inclusive, at screening confirmed by central laboratory analysis.
• Treated with once-daily or twice-daily basal insulin (Neutral Protamine Hagedorn insulin, insulin degludec, insulin detemir, insulin glargine 100 U/mL, or insulin glargine 300 U/mL) ≥ 90 days prior to the day of screening with or without any of the following anti-diabetic drugs/regimens with stable doses greater than equal to (≥) 90 days prior to screening: metformin, sulfonylureas, meglitinides (glinides), Dipeptidyl peptidase 4 (DPP-4) inhibitors, Sodium-Glucose Transport Protein 2 (SGLT2) inhibitors, thiazolidinediones, alphaglucosidase inhibitors, oral combination products (for the allowed individual oral anti- diabetic drugs), oral or injectable glucagon-like peptide 1 receptor agonists (GLP-1 RAs), injectable glucagon-like peptide 1(GLP-1)/ glucose-dependent insulinotropic polypeptide receptor agonist (GIP RA) combination products.
• Body mass index (BMI) ≤ 40.0 kilogram per square meter (kg/m\^2).