This trial is conducted i Europe. The aim of this trial is to test for bioequivalence between two explorative formulations of insulin degludec (insulin 454) and between two explorative insulin degludec/insulin aspart (IDegAsp - formerly SIAC) formulations, all with or without buffer, in healthy male subjects. The investigated formulations are explorative, not similar to the proposed commercial formulation.

Inclusion Criteria:

• Informed consent obtained before any trial-related activities. Trial related activities are any procedure that would not have been performed during the normal management of the subject
• Considered generally healthy upon completion of medical history and physical examination as judged by the Investigator
• Body mass index (BMI) between 18.0 and 27.0 kg/m^2 (inclusive)
• Fasting plasma glucose below or equal to 6 mmol/L
• Sexually active and non-sterilised participants must be informed that they and their partner must use a safe method of contraception during sexual intercourse (risk of pregnancy must be lower than 1%), e.g. implants, injections, combined oral contraceptives or hormonal intrauterinedevice or be willing to refrain from having sexual intercourse from the beginning of the study until up to three months after the conclusion of the study. This serves to exclude the possibilityof a pregnancy through sperm that could have been damaged by the study medication

Exclusion Criteria:

• A history of any illness that, in the opinion of the investigator, might confound the results of the trial or pose risk in administering the trial product to the subject
• Known or suspected allergy to trial products or related products
• Subject who has participated in any other trials involving investigational products within the last 3 months prior to first dosing