Inclusion Criteria:  Diagnosis of type 1 diabetes mellitus for at least 1 year. Male or female participants 18 to 65 years of age. Current use of an insulin pump for at least 3 months with stable insulin pump settings for >2 weeks. HbA1c ≤ 10.5% at screening. Total daily insulin requirement is less than 139 units/day. 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. 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. Hematocrit of less than 36% for men, less than 32% for women. 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 aspart 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). Beta blockers or non-dihydropyridine calcium channel blockers. Current use of any medication intended to lower glucose other than insulin (ex. use of liraglutide). Gastroparesis Any clinically significant disease or disorder which in the opinion of the Investigator may jeopardize the participant's safety or compliance with the protocol.