The purpose of this clinical study is to find out how the novel insulin NNC0363-1063 and a non-glucose carbohydrate used in food and beverage might interact in participants with type 1 diabetes and if co-administration of these substances is safe and tolerable. All participants will get a fixed dose of NNC0363-1063 and an oral administration of different amounts of the non-glucose carbohydrate in a random order during 4 interaction tests. The participants will be in this clinical study for about 5 to 12 weeks.

Inclusion Criteria:

• Male or female participant (sex at birth) of non-child bearing potential. Non-child bearing potential being defined as surgically sterilised (i.e., documented hysterectomy, bilateral salpingectomy or bilateral oophorectomy) or being postmenopausal (defined as no menses for 12 month without an alternative medical cause) prior to the day of screening.
• Age 18-64 years (both inclusive) at the time of signing informed consent.
• Body mass index between 18.5-29.9 Kilogram Per Square Meter (kg/m^2) (both inclusive) at the day of screening.
• Diagnosed with type 1 diabetes mellitus greater than or equal to (≥) 1 year prior to the day of screening.
• Treated with multiple daily insulin injections or continuous subcutaneous insulin infusion ≥ 90 days prior to the day of screening.
• Glycated haemoglobin (HbA1c) less than or equal to (≤ ) 9.0 percentage (%) at the day of screening.

Exclusion Criteria:

• Male of reproductive age who, or whose female partner(s), is not using an adequate contraceptive method.
• Any condition, except for mild conditions under stable treatment associated with type 1 diabetes mellitus, which in the investigator's opinion might jeopardise participant's safety or compliance with the protocol.

According to the Novo Nordisk disclosure commitment on novonordisk-trials.com