New Algorithm for Insulin Delivery in Type 1 Diabetes

Inclusion Criteria: * Diagnosis of type 1 diabetes mellitus for at least 1 year. * Male or female participants 18 and older. * HbA1c or GMI ≥ 7.0% at screening. * Physically willing and able to perform 30 min of exercise (as determined by the investigator after reviewing the participant's activity level). * Current use of an FDA-approved hybrid closed loop system for ≥3 months. * 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 OHSU * Total daily insulin requirement is less than 139 units/day. * Able to read, write and understand spoken English * 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: * GMI or A1c \<6.5% or \>10.5% * Sensor glucose shows \< 2% of time above 250 mg/dl in last 30 days. * Individual 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. * 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 OHSU 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 6 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 (example skin infection requiring antibiotics) * Known or suspected abuse of alcohol, narcotics, or illicit drugs. * Seizure disorder. * Active foot ulceration. * Peripheral arterial disease. * 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 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). * Use of beta blockers or non-dihydropyridine calcium channel blockers. * Current use of any medication that can lower glucose other than insulin (ex. Wegovy, Jardiance) with the exception of metformin if dose has been stable for ≥3 months and patient willing to not change dose during study. * Gastroparesis * Diet consisting of less than 50 grams of carbohydrates per day. * A positive response to any of the questions from the Physical Activity Readiness Questionnaire with one exception: participant will not be excluded if he/she takes a single blood pressure medication that doesn't impact heart rate and blood pressure is controlled on the medication (blood pressure is less than 140/90 mmHg). * Any chest discomfort with physical activity, including pain or pressure, or other types of discomfort. * Any clinically significant disease or disorder which in the opinion of the Investigator may jeopardize the participant's safety or compliance with the protocol.