Screening: After signing a consent form, a screening evaluation will be performed up to 28 days prior to study enrollment in the CRC for the Parts A, B, C or D. The evaluation will consist of medical history, physical examination (including height, weight, vital signs and tanner staging), and blood samples for clinical laboratory tests: CBC, LFTs, amylase, lipase, creatinine and HbA1C. The approximate volume of blood drawn is expected to be 12 ml. CRAFFT questionnaire will be administered. Also each subject will have a Dexcom™ Continuous Glucose Monitoring System inserted. It has three parts - a glucose sensor that is inserted subcutaneously, a transmitter which connects to the sensor electrode and is attached to the body and a receiver which displays the glucose values. It gets updated every 5 minutes. The subject will need to wear it for 7 days. Also, they will be asked to keep a log on diet, insulin and exercise while wearing the CGMS. We will try to schedule the next visit with in the 7 day period while they are on the CGMS so that they are admitted while their glucose levels are relatively stable. We will give an extra sensor with instructions on how to wear it in case they cannot come to the next visit with in the week.