A Research Study to Compare the Effect of Insulin Degludec and Insulin Glargine on Blood Sugar Levels in People With Type 2 Diabetes - the SWITCH PRO Study

Inclusion Criteria: * Male or female, age greater than or equal to 18 years at the time of signing informed consent * Diagnosed with type 2 diabetes mellitus greater than or equal to 180 days prior to the day of screening * Subjects fulfilling at least one of the below criteria: * Experienced at least one severe hypoglycaemic episode within the last year prior to screening (according to the American Diabetes Association definition, January 2018)\* * Moderate renal impairment defined as estimated glomerular filtration rate value of 30-59 mL/min/1.73 m\^2 as defined by Kidney Disease Improving Global Outcomes 2012 at screening * Known hypoglycaemic unawareness as indicated by the investigator according to Clarke's questionnaire question 8 at screening * Treated with insulin for more than 5 years * Episode of hypoglycaemia (defined a glucose alert value of 70 mg/dL (3.9 mmol/L) or less, i.e., Level 1) within the last 12 weeks prior to screening visit * Treated with any basal insulin greater than or equal to 90 days prior to the day of screening with or without any of the following anti-diabetic drugs: * Metformin * Dipeptidyl peptidase-4 inhibitor * Sodium-glucose co-transporter 2 inhibitor * Alpha-glucosidase-inhibitors (acarbose) * Thiazolidinediones * Marketed oral combination products only including the products listed above * HbA1c less than or equal to 9.5% (80 mmol/mol) at screening confirmed by central laboratory analysis * Body mass index less than or equal to 45 kg/m\^2 \*Hypoglycaemia associated with severe cognitive impairment requiring external assistance for recovery Exclusion Criteria: * Treatment with any medication for the indication of diabetes or obesity other than stated in the inclusion criteria within the past 90 days prior to the day of screening. However, intermittent bolus insulin treatment for periods of no longer than 14 days are permitted prior to the day of screening * Anticipated initiation or change in concomitant medications known to affect weight or glucose metabolism (e.g., treatment with orlistat, thyroid hormones, or corticosteroids) * Uncontrolled and potentially unstable diabetic retinopathy or maculopathy. Verified by a pharmacologically pupil-dilated fundus examination performed by an ophthalmologist or another suitably qualified health care provider within the past 90 days prior to screening or in the period between screening and run-in