Patient description: The patient is a 24-year-old man who has had type 1 diabetes for 11 years. He presents to the emergency room with hyperglycemia and concern for possible diabetic ketoacidosis after not taking his insulin for 3 days. The patient reports that he is currently homeless and has lost his supply of insulin, syringes, glucometer, and glucose testing supplies. The patient states that at the time of his initial diagnosis with type 1 diabetes he was hospitalized with a glucose value >1000 mg/dL. At the time, he was experiencing polyuria, polydipsia, and polyphagia. He reports that he has been on insulin since the time of his diagnosis, and he has never been prescribed oral agents for diabetes management. Most recently, he has been using insulin glargine 55 units once daily, and insulin aspart sliding scale 3 times daily. The patient has had previous episodes of diabetic ketoacidosis, for which he was hospitalized. With this episode of hyperglycemia, he is not experiencing any nausea, vomiting, or abdominal discomfort, and he appears well. His lab studies showed: A1c: 11.3% Creatinine: 0.9 mg/dL with eGFR >60 mL/min Aspartate aminotransferase (AST): 17 U/L Alanine aminotransferase (ALT): 14 U/L Beta-hydroxybutyrate: 0.1 mmol/L Bicarbonate: 25 mEq/L Anion

Clinical trial eligibility criteria: eligible ages (years): 21.0-65.0,  Type 1 Diabetes Mellitus ≥21 and <65 years old 2. Clinical diagnosis of type 1 diabetes mellitus for documented hyperglycemia (at least 1 criterion must be met) Fasting glucose ≥126 mg/dL confirmed Two-hour Oral Glucose Tolerance Test (OGTT) glucose ≥200 mg/dL confirmed HbA1c ≥6.5% documented by history confirmed Random glucose ≥200 mg/dL with symptoms No data at diagnosis is available but the participant has a convincing history of hyperglycemia consistent with diabetes  Diabetic ketoacidosis within the 6 months prior to enrollment 2. Severe hypoglycemia resulting in seizure, loss of consciousness, or 3rd party assistance in the 12 months prior to enrollment 3. Subject reports that he/she has hypoglycemia unawareness with severe low blood sugars (e.g. <50 mg/dL without symptoms) 4. Pregnancy; breast feeding, or intention of becoming pregnant 5. Uncontrolled arterial hypertension (diastolic blood pressure >90 mmHg and/or systolic blood pressure >160 mmHg) 6. Conditions which may increase the risk of hypoglycemia such as any cardiac disorder/arrhythmia, uncontrolled coronary artery disease during the previous year (e.g. history of myocardial infarction, acute coronary syndrome, therapeutic coronary intervention, coronary bypass or stenting procedure, stable or unstable angina, episode of chest pain of cardiac etiology with documented EKG changes, or positive stress test or catheterization with coronary blockages >50%), congestive heart failure, history of cerebrovascular event, seizure disorder, syncope, adrenal insufficiency, neurologic disease or atrial fibrillation 7. Hematocrit <40% (males) and <35% (females) 8. History of a systemic or deep tissue infection with methicillin-resistant staph aureus or Candida albicans 9. Use of a device that may pose electromagnetic compatibility issues and/or radiofrequency interference with the CGM (implantable cardioverter-defibrillator, electronic pacemaker, neurostimulator, intrathecal pump, and cochlear implants) 10. Anticoagulant therapy other than aspirin 11. Oral steroids 12. Medical condition requiring use of an acetaminophen-containing medication that cannot be withheld for the study admissions. 13. Psychiatric disorders that would interfere with study tasks (e.g. inpatient psychiatric treatment within 6 months prior to enrollment) 14. Mental incapacity, unwillingness or language barriers precluding adequate understanding or cooperation 15. Known current or recent alcohol or drug abuse 16. Medical conditions that would make operating a CGM, cell phone, or insulin pump difficult (e.g. blindness, severe arthritis, immobility) 17. Any skin condition that prevents sensor or pump placement on the abdomen or arm (e.g. bad sunburn, pre-existing dermatitis, intertrigo, psoriasis, extensive scarring, cellulitis) 18. Impaired hepatic function measured as alanine aminotransferase or aspartate aminotransferase ≥three times the upper reference limit 19. Impaired renal function measured as creatinine >1.2 times above the upper limit of normal 20. Uncontrolled microvascular (diabetic) complications (other than diabetic non-proliferative retinopathy), such as current proliferative diabetic retinopathy, known diabetic nephropathy (other than microalbuminuria with normal creatinine) or neuropathy requiring treatment 21. Active gastroparesis requiring current medical therapy 22. If taking antihypertensive, thyroid, anti-depressant or lipid lowering medication, lack of stability on the medication for the past 2 months prior to enrollment in the study 23. Uncontrolled thyroid disease 24. Known bleeding diathesis or dyscrasia 25. Known allergy to medical adhesives, components of the insulin pump insertion set or continuous glucose monitor sensor 26. Active enrollment in another clinical trial 27. Unwillingness to withhold dietary supplements two weeks prior to admission and for the duration of the study participation 28. Use of anti-diabetic agents other than CSII including long-acting insulin, intermediate-acting insulin, metformin, sulfonylureas, meglitinides, thiazolidinediones, DPP-IV inhibitors, glucagon-like peptide 1 agonists, and alpha-glucosidase inhibitors 29. Subjects with basal rates less than 0.05. ON USE OF OTHER DRUGS OR 1. Use of anti-diabetic agents other than CSII including long-acting insulin, intermediate-acting insulin, metformin, sulfonylureas, meglitinides, thiazolidinediones, DPP-IV inhibitors, glucagon-like peptide 1 agonists, and alpha-glucosidase inhibitors. 2. Oral steroids are excluded 3. Anticoagulant therapy other than aspirin is excluded 4. Acetaminophen will not be allowed while the continuous glucose monitor is in use 5. Dietary supplements will be withheld two weeks prior to admission and for the duration of study participation 6. Medications that block symptoms of hypoglycemia, including but not limited to beta blockers