Sitagliptin in Type I Diabetic Patients

Inclusion Criteria: 1. Male or female adult, aged 18 to 70 years 2. Type 1 Diabetes Mellitus for 6 months or more, as established by medical history 3. Current treatment with multiple injections of insulin (at least 4) or CSII (continuous subcutaneous insulin infusion or insulin pump) therapy for at least 3 months prior to screening visit; and using the same insulin during the last 1 month 4. HbA1c ≤ 8.5% 5. Subjects should routinely practice at least 2-4 blood glucose measurements per day 6. BMI ≤ 35 kg/m2 7. Subject must be able and willing to perform self-blood glucose monitoring and accept wearing a continuous glucose monitor for 3 days at the start and 3 days at the end of the study 8. Subjects must be willing to complete study visits per study protocol 9. Able to speak, read, and write English Exclusion Criteria: 1. Type 1 Diabetes Mellitus for less than 6 months 2. Coronary Event or procedure (myocardial infarction, unstable angina, coronary artery bypass surgery, or coronary angioplasty) in the previous 4 weeks 3. Any other life-threatening, non-cardiac disease 4. Pregnant or intends to become pregnant during the course of the study 5. Severe unexplained hypoglycemia that required emergency treatment over the past 3 months 6. History of hemoglobinopathies 7. Post-renal transplantation, currently undergoing dialysis, creatinine of \>1.5mg/dl or a calculated creatinine clearance of \<50 mL/min. 8. Have extensive skin changes/diseases that inhibit wearing the sensor on normal skin 9. Subjects who have an allergy to medication being used 10. Current participation in another study protocol 11. History of autonomic neuropathy or gastroparesis