This study will be looking to confirm the effect of dasiglucagon when compared with glucagon for treating very low sugar levels in Asian adults with T1D and the effect of dasiglucagon in Japanese adolescents with T1D. This study wants to demonstrate that dasiglucagon can raise low blood sugar levels just as well as glucagon. Participants will get dasiglucagon and glucagon. In which treatment order participants get study medicines (dasiglucagon and glucagon) is decided by chance. Dasiglucagon is a new medicine, but doctors can prescribe it in the US as it is approved there. Doctors can prescribe glucagon in multiple countries including Japan as an approved medicine. The study will last for about 17 weeks. Participant cannot be in the study if the study doctor thinks that there are risks for participants health. Women cannot take part if pregnant, breast-feeding, plan to get pregnant, during the study period, or not using adequate contraceptive methods. For man: if participant have sex, participant and his partner must use an adequate birth control method during the study.

Inclusion Criteria:

• For Adults: Asian male or female; For Adolescents: Japanese male or female.
• Age at the time of signing the informed consent:

For Adults: Age 18-75 years (both inclusive):

For Adolescents: Age 12-15 years (both inclusive).

• Diagnosed with T1D greater than (>)1 year before screening.
• Glycated haemoglobin (HbA1c) less than (<)10.0 percentage (%) (86 millimoles per mole [mmol/mol]) as assessed by subcontracted laboratory by the site on the day of screening.
• For adults: BMI between 18.5 and 29.9 kilogram per meter square (kg/m2) (both inclusive).

For adolescents: Body weight greater than or equal to (≥) 33.4 kilograms (kg).

• Treated with stable insulin treatment (based on the investigator's discretion preferably no more than a 10-unit daily variation in total daily insulin dose) 30 days prior to screening.
• For Japanese participants: Japanese passport or equivalent For non-Japanese participants: Asian (non- Japanese passport or equivalent).

Exclusion Criteria:

• Known or suspected hypersensitivity to study intervention(s) or related products (glucagon or its derivatives).
• Exposure to an investigational medicinal product (IMP) within 30 days or 5 times the half-life of the IMP (if known), whichever is longest before screening.
• Severe hypoglycaemia in the last month prior to screening.
• Hospitalisation for diabetic ketoacidosis (DKA) in the last month prior to screening.
• Presence or history of any clinically relevant respiratory, metabolic, renal, hepatic, gastrointestinal, endocrinological conditions (except conditions associated with diabetes mellitus).
• History of epilepsy or seizure disorder.
• Known presence or history of pheochromocytoma (i.e., adrenal gland tumour) or insulinoma (i.e., insulin-secreting pancreas tumour).
• Clinically significant abnormal electrocardiogram (ECG) at screening as evaluated by investigator.
• Any disorder, unwillingness or inability which in the investigator's opinion, might jeopardise the participant's safety or compliance with the protocol.

As declared by the participant or in the medical records.

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