Patient description: The patient is a 24-year-old man who has had type 1 diabetes for 11 years. He presents to the emergency room with hyperglycemia and concern for possible diabetic ketoacidosis after not taking his insulin for 3 days. The patient reports that he is currently homeless and has lost his supply of insulin, syringes, glucometer, and glucose testing supplies. The patient states that at the time of his initial diagnosis with type 1 diabetes he was hospitalized with a glucose value >1000 mg/dL. At the time, he was experiencing polyuria, polydipsia, and polyphagia. He reports that he has been on insulin since the time of his diagnosis, and he has never been prescribed oral agents for diabetes management. Most recently, he has been using insulin glargine 55 units once daily, and insulin aspart sliding scale 3 times daily. The patient has had previous episodes of diabetic ketoacidosis, for which he was hospitalized. With this episode of hyperglycemia, he is not experiencing any nausea, vomiting, or abdominal discomfort, and he appears well. His lab studies showed: A1c: 11.3% Creatinine: 0.9 mg/dL with eGFR >60 mL/min Aspartate aminotransferase (AST): 17 U/L Alanine aminotransferase (ALT): 14 U/L Beta-hydroxybutyrate: 0.1 mmol/L Bicarbonate: 25 mEq/L Anion

Clinical trial eligibility criteria: eligible ages (years): 6.0-999.0,  Type 1 Diabetes Mellitus Cognitive Change Clinical diagnosis, based on investigator assessment, of type 1 diabetes for at least one year, using insulin for at least 1 year and using an insulin pump for at least 6 months Familiarity and use of a carbohydrate ratio for meal boluses by participants and families participating Age 6-10 years old or 65 years or older Hemoglobin A1c <10% For females of child-bearing potential, not currently known to be pregnant: A negative serum or urine pregnancy test will be required for all females of child-bearing potential. Participants who become pregnant will be discontinued from the study. Also, participants who during the study develop and express the intention to become pregnant within the timespan of the study will be discontinued For participants <18 years old, living with one or more parent/legal guardian knowledgeable about emergency procedures for severe hypoglycemia and able to contact the participant in case of an emergency Willing to disable any automated insulin delivery functionality on a personal insulin pump during study, such as Medtronic 670G in auto mode. Predictive low blood glucose suspend, such as Tandem insulin pump with Basal-IQ, will be allowed Investigator has confidence that the participant and family can successfully operate all study devices and is capable of adhering to the protocol Willingness to switch to lispro (Humalog) or aspart (Novolog) and to use no other insulin besides lispro (Humalog) or aspart (Novolog) during the study Total daily insulin dose (TDD) at least 10 U/day  Severe hypoglycemia resulting in seizure or loss of consciousness in the 12 months prior to enrollment Diagnosis of Diabetic Ketoacidosis in the 12 months prior to enrollment Uncontrolled cardiac disease (e.g. recent myocardial infarction, severe congestive heart failure) Cerebrovascular accident in the 12 months prior to enrollment Uncontrolled resting arterial hypertension (>160/90 mm Hg) Conditions that would make use of a CGM difficult (e.g., blindness, severe arthritis, immobility) Current use of oral/inhaled glucocorticoids or other medications, which in the judgment of the investigator would be a contraindication to participation in the study Concurrent use of any non-insulin glucose-lowering agent other than metformin (including GLP-1 agonists, pramlintide, DPP-4 inhibitors, SGLT-2 inhibitors, sulfonylureas) Hemophilia or any other bleeding disorder A condition, which in the opinion of the investigator or designee, would put the participant or study at risk