This trial is conducted in Europe. The aim of this trial is to investigate if liraglutide adjunct to insulin treatment changes the glucagon response during hypoglycaemia in subjects with type 1 diabetes compared with conventional insulin treatment after 4 weeks' treatment with liraglutide or placebo.

Subjects will initially be randomised to one of the three dose groups, and subsequently randomly allocated to one of two treatment sequences (liraglutide/placebo or placebo/liraglutide).

Inclusion Criteria:

• Type 1 diabetes mellitus (as diagnosed clinically) for at least 12 months prior to randomisation
• Body mass index (BMI) between 20.0 and 28.0 kg/m^2 (both inclusive)

Exclusion Criteria:

• Use of liraglutide or exenatide within 3 months of randomisation
• Recurrent severe hypoglycaemia (more than 1 severe hypoglycaemic event during the last 12 months) or hypoglycaemic unawareness as judged by the trial physician or hospitalisation for diabetic ketoacidosis during the previous 6 months
• Subject who has donated any blood or plasma in the past month or more than 500 mL within 3 months prior to screening