Inclusion Criteria:
* Age ≥18 years old at time of screening.
* Currently resides in the U.S. or Canada with the ability to complete in-person study visits at one of the participating clinical sites.
* Clinical diagnosis, based on investigator assessment, of type 2 diabetes of at least 6 months duration at time of screening.
* Using basal-bolus insulin therapy with at least one injection containing rapid-acting insulin per day or an insulin pump for at least 3 months prior to enrollment, with no major modification to insulin regime in the last 3 months (mixed insulin with a rapid component is acceptable).
* If using noninsulin glucose-lowering medications (such as GLP-1 receptor agonist, SGLT2 inhibitor, or other) or weight-reduction medications, dose has been stable for the 3 months prior to screening; and participant is willing to not change the dose unless required for safety purposes.
* Participant willing to not initiate use of any new glucose-lowering medications during the trial.
* Willing to use an approved insulin while using the study pump if assigned to the AID group.
* Willing to not use concentrated insulin above U-100 or inhaled insulin while using the study pump.
* Willing to participate in the study meal and exercise challenges if assigned to the AID group, and have a care partner, trained in hypoglycemia treatment guidelines, to include glucagon use, present during and immediately after the exercise challenges.
* Has the ability to read and understand written English.
* Investigator believes that the participant has the cognitive capacity to provide informed consent.
* Investigator believes that the participant can successfully and safely operate all study devices and is capable of adhering to the protocol and completing the study.
* No medical, psychiatric, or other conditions, or medications being taken that in the investigator's judgement would be a safety concern for participation in the study. This includes considering the potential impact of medical conditions known to be present including cardiovascular, liver, kidney disease, thyroid disease, adrenal disease, malignancies, vision difficulties, active proliferative retinopathy, and other medical conditions; psychiatric conditions including eating disorders; drug or alcohol abuse.
* Participants capable of becoming pregnant must meet one of the following criteria:
1. has a negative urine pregnancy test and agrees to use one of the accepted contraceptive regimens throughout the entire duration of the trial from screening until last follow-up visit. The following contraceptive measures are considered adequate:
1. Combined estrogen and progestogen containing hormonal contraception associated with inhibition of ovulation (oral, intravaginal, transdermal).
2. Progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable, implantable).
3. Placement of an intrauterine device or intrauterine hormone-releasing system.
4. Bilateral tubal occlusion.
5. Barrier methods of contraception (condom or occlusive cap with spermicidal foam/gel/film/cream/suppository).
6. Has a vasectomized or sterile partner (where partner is sole partner of subject) and where vasectomy has been confirmed by medical assessment.
7. Exercises true sexual abstinence. Sexual abstinence is defined as refraining from heterosexual intercourse during the entire period of risk associated with the study treatments. The reliability of sexual abstinence needs to be evaluated in relation to the duration of the clinical trial and the preferred and usual lifestyle of the subject.
or
2. Participant is of non-childbearing potential due to menopause with at least one year since last menses or a medical condition confirmed by the investigator.
Exclusion Criteria:
* Current use of hybrid closed-loop system.
* Current use of systemic glucocorticoids or anticipated use of glucocorticoids during the RCT (topical or inhaled -ie, non-systemic is acceptable).
* Current use of sulfonylurea or meglitinide medications.
* Current use of hydroxyurea.
* Tape allergy or skin condition that will preclude use of the study pump or CGM.
* Presence of a hemoglobinopathy or other condition that is expected to affect the measurement of HbA1c.
* Pregnant (positive urine hCG), breast feeding, plan to become pregnant in the next 2 months, or sexually active without use of contraception.
* Current participation in another diabetes-related interventional clinical trial.
* Anticipated change of residency or travel for more than 7 days at a time during the study that may, per investigator judgment, interfere with the completion of study visits, contacts, or procedures.
* Immediate family member (spouse, biological or legal guardian, child, sibling, parent) who is an investigative site personnel directly affiliated with this study or who is an employee of Tandem Diabetes Care, Inc.
