The Pediatric Artificial Pancreas Automated Initialization Trial

Inclusion Criteria: 1. Clinical diagnosis, based on investigator assessment, of type 1 diabetes for at least 1 month 2. Familiarity and use of a carbohydrate ratio for meal boluses 3. Age ≥2 and \<6 years old 4. Using a Dexcom CGM at the time of enrollment, with use on at least 21 out of the prior 28 days 5. Living with one or more parent/legal guardian knowledgeable about emergency procedures for severe hypoglycemia and able to contact emergency services and study staff 6. Parent/guardian has a phone that can run the Tandem t:connect Mobile App (typically Android 10 or above or iPhone Operating System (iOS) 15 or above) 7. Willingness to use the t:connect Mobile App as needed during the study and ensure connectivity for a data upload at least once per day 8. Investigator has confidence that the parent can successfully operate all study devices and is capable of adhering to the protocol 9. Willingness to switch to lispro (Humalog) or aspart (Novolog) if not using already, and to use no other insulin besides lispro (Humalog) or aspart (Novolog) during the study for participants using a study162 provided Tandem pump during the study 10. Total daily insulin dose (TDD) at least 5 Units/day 11. Body weight at least 20 pounds (lbs) 12. Willingness not to start any new non-insulin glucose-lowering agent during the course of the trial 13. Participant and parent(s)/guardian(s) willingness to participate in all training sessions as directed by study staff 14. Parent/guardian proficient in reading and writing English 15. Live in the United States, with no plans to move outside the United States during the study period Exclusion Criteria: 1. Concurrent use of any non-insulin glucose-lowering agent (including GLP-1 agonists, Symlin, DPP-4 inhibitors, SGLT-2 inhibitors, sulfonylureas) 2. Hemophilia or any other bleeding disorder 3. History of \>1 severe hypoglycemic event with seizure or loss of consciousness in the last 3 months 4. History of \>1 diabetic ketoacidosis (DKA) event in the last 6 months not related to illness, infusion set failure, or initial diagnosis 5. History of chronic renal disease or currently on hemodialysis 6. History of adrenal insufficiency 7. Hypothyroidism that is not adequately treated in the opinion of the investigator 8. Use of oral or injectable steroids within the last 8 weeks 9. Known, ongoing adhesive intolerance 10. Plans to receive blood transfusions or erythropoietin injections during the course of the study 11. A condition, which in the opinion of the investigator or designee, would put the participant or study at risk 12. Participation in another pharmaceutical or device trial at the time of enrollment or during the study 13. Having immediate family members employed by Tandem Diabetes Care, Inc. or Dexcom, Inc., or having a direct supervisor at place of employment who is also directly involved in conducting the clinical trial (as a study investigator, coordinator, etc.); or having a first-degree relative who is directly involved in conducting the clinical trial