This trial was conducted in Europe. The aim of this clinical trial was to evaluate the pharmacodynamic dose-response relationship of NN5401 (insulin degludec/insulin aspart) at three therapeutically relevant doses in subjects with type 1 diabetes.

The trial is designed as a four period, incomplete block cross-over trial where the trial participant will be randomised to a treatment sequence by which the subject will receive two matched dose levels of NN5401 and biphasic insulin aspart, respectively.

Inclusion Criteria:

• Type 1 diabetes mellitus (as diagnosed clinically) for at least 12 months
• Body mass index 18.0-28.0 kg/m^2 (both inclusive)

Exclusion Criteria:

• Subject who has donated any blood or plasma in the past month or more than 500 mL within 3 months prior to screening
• Smoker (defined as a subject who is smoking more than 5 cigarettes or the equivalent per day)
• Supine blood pressure at screening (after resting for 5 min) outside the range of 90-140 mmHg for systolic or 50-90 mmHg for diastolic
• Not able or willing to refrain from smoking and use of nicotine gum or transdermal nicotine patches during the inpatient period