This case study focuses on John Smith, a 68-year-old male with Type 2 Diabetes Mellitus, examining the physiological aspects of blood glucose control, consequences of hyperglycemia, and the use of Metformin for diabetes management. It compares John's condition to a non-diabetic individual, highlighting insulin production and resistance. The study further explores the impact of high blood glucose levels, such as retinopathy and angina pectoris, and explains how Metformin aids in increasing insulin sensitivity and reducing glucose production in the liver. Additionally, it delves into the pathophysiology of insulin resistance due to increased abdominal adiposity and discusses the role of HbA1c in long-term blood glucose management. The analysis is supported by relevant references and an annotated bibliography.