A Research Study to Look at How Faster Aspart Works in Chinese People With Type 1 Diabetes or Type 2 Diabetes

Inclusion criteria: For a subject with type 1 diabetes mellitus: * Male or female Chinese subjects aged 18-64 years (both inclusive) at the time of signing informed consent. * Type 1 diabetes mellitus (as diagnosed clinically) greater than or equal to 12 months prior to the day of screening. * Treated with multiple daily insulin injections or premix insulin greater than or equal to 12 months prior to the day of screening or treated with continuous subcutaneous insulin infusion (CSII) greater than or equal to 3 months prior to the day of screening. * Glycosylated haemoglobin (HbA1c) less than or equal to 9.0 percent (75 mmol/mol) by central laboratory analysis. For a subject with type 2 diabetes mellitus: * Male or female Chinese subjects aged 18-75 years (both inclusive) at the time of signing informed consent. * Type 2 diabetes mellitus (as diagnosed clinically) greater than or equal to 12 months prior to the day of screening. * Treated with multiple daily insulin injections or premix insulin greater than or equal to 6 months prior to the day of screening or treated with continuous subcutaneous insulin infusion (CSII) greater than or equal to 3 months prior to the day of screening. * Glycosylated haemoglobin less than or equal to 9.5 percent (80 mmol/mol) by central laboratory analysis. Exclusion criteria: For a subject with type 1 diabetes mellitus or type 2 diabetes mellitus: * Any disorder, which in the investigator's opinion might jeopardise subject's safety or co…