Two Way Crossover Closed Loop MPC vs Control IQ

Inclusion Criteria: * Diagnosis of type 1 diabetes mellitus for at least 1 year. * Age 18 years and older. * Current use of a t:slim X2 insulin pump with Dexcom G6 with the use of Control IQ for at least 12 weeks. * Willingness to use Fiasp insulin during intervention study * Lives with another person age 18 or older who will sleep in the house at night and that can attend the training on using the system. * Lives within 40 miles of enrollment site. * HbA1c ≥ 7.5% at screening. * Total daily insulin requirement is less than 139 units/day. * Current use of a smartphone so can be contacted by study staff off-campus * Willingness to follow all study procedures, including attending all clinic visits. * Willingness to sign informed consent and HIPAA documents. Exclusion Criteria: * Female of childbearing potential who is pregnant or intending to become pregnant or breast-feeding, or is not using adequate contraceptive methods. Acceptable contraception includes birth control pill / patch / vaginal ring, Depo-Provera, Norplant, an IUD, the double barrier method (the woman uses a diaphragm and spermicide and the man uses a condom), or abstinence. * HbA1c \>10% at screening. * Any cardiovascular disease, defined as a clinically significant EKG abnormality at the time of screening or any history of: stroke, heart failure, myocardial infarction, angina pectoris, or coronary arterial bypass graft or angioplasty. Diagnosis of 2nd or 3rd degree heart block or any non-physiological arrhythmia judged by the investigator to be exclusionary. * Renal insufficiency (GFR \< 60 ml/min, using the MDRD equation as reported by the site laboratory). * Liver failure, cirrhosis, or any other liver disease that compromises liver function as determined by the investigator. * History of severe hypoglycemia during the past 12 months prior to screening visit or hypoglycemia unawareness as judged by the investigator. Participants will complete a hypoglycemia awareness questionnaire. Participants will be excluded for four or more R responses. * History of diabetes ketoacidosis during the prior 6 months prior to screening visit, as diagnosed on hospital admission or as judged by the investigator. * Adrenal insufficiency. * Any active infection. * Known or suspected abuse of alcohol, narcotics, or illicit drugs. * Seizure disorder. * Active foot ulceration. * Severe peripheral arterial disease characterized by ischemic rest pain or severe claudication. * Major surgical operation within 30 days prior to screening. * Use of an investigational drug within 30 days prior to screening. * Chronic usage of any immunosuppressive medication (such as cyclosporine, azathioprine, sirolimus, or tacrolimus). * Bleeding disorder, treatment with warfarin, or platelet count below 50,000. * Allergy to Fiasp insulin. * Current administration of oral or parenteral corticosteroids. * Any life-threatening disease, including malignant neoplasms and medical history of malignant neoplasms within the past 5 years prior to screening (except basal and squamous cell skin cancer). * Current use of beta blockers or non-dihydropyridine calcium channel blockers. * Current use of any medication intended to lower glucose other than insulin (ex. use of metformin or liraglutide). * Gastroparesis * Low carbohydrate diet at the time of screening defines as less than 50 grams of carbohydrate per day. * Any clinically significant disease or disorder which in the opinion of the Investigator may jeopardize the participant's safety or compliance with the protocol.