The purpose of this study is to see if the use of metformin and sitagliptin used in conjunction with insulin can improve the blood sugars of teenagers with Type 1 diabetes.

• The study will include a total of 4 visits. The time period between the very first visit and the very last visit will be between 10 and 15 weeks. Each participant will be randomized to one of the 3 groups in the study. The groups are as follows:
• Group 1: Insulin and sitagliptin
• Group 2: Insulin and metformin
• Group 3: Insulin and combination of sitagliptin and metformin
• The study is a randomized open label design. All subjects will undergo a screening visit; if inclusion and exclusion criteria are fulfilled they will be enrolled in the study. At the time of enrollment the subject will continue their home insulin regimen and will be randomized to an add an oral hypoglycemic agent(s) : metformin, sitagliptin or combination therapy (metformin and sitagliptin). The total duration on study medication will be 6 weeks. All subjects will undergo a baseline mixed meal tolerance test (MMTT) in their standard or usual insulin Each subject will undergo a total of two studies. Blood draws will be necessary.

Inclusion Criteria:

• Age of 13 to 18 years
• HbA1c >7.5% but <10%
• Subjects must be on intensive insulin management
• Tanner stage greater than or equal to 4
• Must have T1DM for at least one year , T1DM defined by ADA criteria and having at least one of the following antibodies: Anti-GAD, Anti-islet, Anti-insulin
• C-peptide > 0.6 ng/ml

Exclusion Criteria:

• Type 2 diabetes
• History of any other chronic condition (except hypothyroidism stable on medications)
• Actively taking medications that may affect glucose excursions (steroids or oral contraceptives)
• Evidence of anemia, clinically significant elevation of the liver enzymes (3 X normal), amylase or lipase (2 X normal), abnormal triclycerides (3 X normal), abnormal renal function test
• An unsupportive family environment and pregnant or lactating females