There is no definitive study on how long type 1 diabetes lasts, and it needs to be analyzed on an individual basis. If blood glucose is actively controlled and there are no serious complications, survival is generally not affected; if blood glucose is not well controlled or serious complications are induced, survival will be shortened, and may lead to death if acute complications are induced. Once diagnosed with type 1 diabetes mellitus, one should follow the doctor’s instructions to use insulin injections, and at the same time with dietary control, such as controlling total calorie intake, avoiding oily and high-calorie foods, etc., and appropriate physical exercise; through the above methods, patients with type 1 diabetes mellitus with blood glucose control within a reasonable range and without serious complications generally do not affect the life expectancy. However, if they do not actively control their blood glucose, long-term poor glycemic control may lead to cardiovascular disease, renal disease and other serious complications, which may shorten their survival; if acute complications such as diabetic ketoacidosis are induced, they may even threaten their lives, and may die if they are not resuscitated in time. Patients diagnosed with type 1 diabetes mellitus should actively cooperate with their doctors and maintain a healthy lifestyle to help improve their prognosis.