A Research Study of How Different Doses of a New Medicine NNC0148-0287 C (Insulin 287) Work on the Blood Sugar in People With Type 1 Diabetes When it is Taken Once a Week

This study compares the new long-acting insulin 287 with the marketed insulin glargine for use in type 1 diabetes. The study will test how insulin is taken up in your blood, how long it stays there and how the blood sugar is lowered. The participant will get both of the insulins in a random order. Insulin 287 is a new medicine while insulin glargine is already approved for the treatment of diabetes and can be prescribed by a doctor. The participant will get 8 weekly doses of insulin 287 and 14 daily doses of insulin glargine. There will also be a run-in period of 2 days to 4 weeks with daily doses of insulin glargine before you start the insulin 287 period. All doses will be injected under the skin. The study will last for about 16 to 24 weeks. The participant will have 27 visits with the study doctor.