A Study to Look at How Safe Insulin NNC0471-0119 is and How it Works in People With Type 1 Diabetes Mellitus

This study is looking at the safety of the new medicine, insulin NNC0471-0119, its concentrations in the blood and effect on blood sugar for the treatment of type 1 diabetes. Insulin NNC0471-0119 will be compared to faster aspart. The purpose of this study is to test how insulin NNC0471-0119 is tolerated by participants body, how it is transported in participants bloodstream, how long it stays there and how the blood sugar is lowered compared to faster aspart. Participants will get either the new insulin NNC0471-0119 or faster aspart-which treatment participants get is decided by chance. It is the first time insulin NNC0471-0119 is tested in people. Faster aspart is a globally used medication for treatment of diabetes mellitus. Participants will get one single injection in a fasting state which will take place at the study site. The medicine will be injected under the skin in the stomach. The study will last for about 13-53 days, depending on individual visit schedule. Participants will have four clinic visits with the study doctor, one of which will require an in-house visit period of 3 days. During the in-house visit, two intravenous cannulas will be inserted for sampling of blood and infusion of insulin. Participants cannot be in the study if the study doctor thinks that there are risks to their health. Women: Women cannot take part if they are of childbearing potential.