A Research Study Looking at How Faster Aspart Injected in Double Concentration Works in the Body of People With Type 1 Diabetes Mellitus

This study is looking at how five different formulations of faster aspart 200 U/mL reach and stay in the blood after injection. The purpose is to find a formulation that behaves similarly to the reference product called faster aspart 100 U/mL (marketed as Fiasp®). The participant will get all five formulations and the reference product. The order in which the participant gets them is decided by chance. The participant will get each medicine once during the study meaning that the participant will get a total of six injections with study medicine. The medicine will be injected under the skin in the stomach. The study will last for about 2 to 21 weeks depending on individual visit schedule. The participant will have nine clinic visits with the study doctor (including the one in which the participant give consent).