This trial is conducted in Europe. The aim of this trial is to investigate the pharmacodynamic (the effect of the investigated drug on the body) of insulin degludec (insulin 454), an explorative formulation, not similar to the proposed commercial formulation, under single-dose and steady-state conditions in male subjects with type 1 diabetes.

Inclusion Criteria:

• Male and are considered to be generally healthy, except for the underlying diabetes mellitus, based on an assessment of medical history, physical examination and clinical laboratory data, as judged by the Investigator
• Diagnosed with type 1 diabetes mellitus and treated with insulin for at least 12 months
• Body Mass Index (BMI) between 18.0 and 27.0 kg/m^2 (both inclusive)
• Glycosylated haemoglobin A1c (HbA1c) below or equal to 10.0 % based on central laboratory results

Exclusion Criteria:

• History of significant multiple drug allergies or with a known or suspected allergy to the trial product or any medicine chemically related to the trial product, as judged by the Investigator
• Participation in any other trials involving investigational products within 3 months preceding the start of dosing