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 Informed Consent 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 gastr…