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): 18.0-999.0,  Li-Fraumeni Syndrome All TP53 germline mutation positive adult patients will be eligible for this study. All patients must have a documented TP53 germline mutation Patients with history of cancer must be in remission, with surgery completed at least 6 months prior to enrollment and chemotherapy completed at least 1 year prior to enrollment (except for basel cell carcinoma of the skin) Age greater than or equal to 18 years. The doses of metformin used in this study exceed the maximum recommended daily dose for the pediatric population ECOG performance status 0 or 1 or Karnofsky greater than or equal to 70% Patients must have normal organ and marrow function as defined below Leukocytes*: greater than or equal to 3,000/microL* Absolute neutrophil count: greater than or equal to 1,500/ microL Platelets: greater than or equal to 100,000/ microL Total bilirubin: Within normal institutional limits AST(SGOT) / ALT(SGPT): less than or equal to 2.5 times institutional upper limit of normal  Patients who have had stem-cell transplantation Current use of metformin or other anti-diabetic agents, or hypersensitivity or allergy to metformin Patients who are receiving any other investigational agents Patients with history of chronic alcohol use History of allergic reactions attributed to compounds of similar chemical or biologic composition to metformin or other agents used in study Patients with congestive heart failure requiring pharmacological management Uncontrolled inter-current illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements for 13C-MBT for 13C-MBT studies in addition to general (pertaining to effects of oral uptake of the administered substrate or mitochondrial function in the liver)