Extended Bolus for Meals in a Closed-loop System

Inclusion Criteria - Age between 13 and 19 years old, A1C \> 6% at screening - Diagnosed with type 1 diabetes for at least one year - Total daily dose (TDD) of insulin ≥ 0.3 units/kg/day - Currently using the Control IQ closed-loop system - Willing to abide by meal recommendations and study procedures - Willing and able to sign the willing to sign a consent form Form (ICF) and/or has a parent or guardian willing and able to sign the ICF - Use an Android or Apple smartphone - Willingness not to start any new non-insulin glucose-lowering agent during the course of the trial - Participant and parent(s)/guardian(s) willingness to participate in all training sessions as directed by study staff - Parent/guardian proficient in reading and writing English - Live in the United States, with no plans to move outside the United States during the study period Exclusion Criteria - A1C \>10% - One or more episodes of severe hypoglycemia or DKA requiring ER visit or hospitalization within the past three months - Used non-insulin anti-diabetic medication within the last 30 days other than metformin - Known history of gastroparesis, seizure disorder, adrenal insufficiency, or ongoing renal or hepatic disease - Pregnancy or lactation - Untreated or unstable hypothyroidism - Currently undergoing cancer treatment or systemic treatment with steroids - Untreated or inadequately treated mental illness - Current alcohol abuse - Current illness that would interfere with participation in the study - Delayed gastric emptying or any concurrent conditions that can be associated with delayed gastric emptying or altered digestion; and the use of any medication that affects gastric emptying - Celiac Disease Always talk to your doctor about whether this trial is right for you.