This study looks at how faster aspart reaches and stays in the blood after injection in Chinese people with type 1 diabetes or type 2 diabetes, compared to the reference product called NovoRapid®. Participants will get both faster aspart and NovoRapid®. The order in which Participants get them is decided by chance. Participants will get each study medicine once during the study meaning that they will get a total of 2 injections with study medicines. The medicine will be injected under the skin of the lower abdomen. The study will last for about 19-72 days. Participants will have 5 clinic visits with the study doctor (including the one in which participants give their consent). Participants will need to stay overnight for 2 of the 5 clinic visits. Participants will have blood samples taken during some of the clinic visits. During the visits where participants get the study medicines, samples of their blood will be taken several times for up to 12 hours after getting the study medicine.

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 compliance with the protocol.
• Surgery or trauma with significant blood loss (more than 400 mL) within the last 3 months prior to screening.
• Not able or willing to refrain from smoking and use of nicotine substitute products during the in-patient period.

According to the Novo Nordisk disclosure commitment on novonordisk-trials.com

Sponsor staff involved in the clinical trial is masked according to company standard procedures.