This review discusses the pathophysiology of Type 2 Diabetes Mellitus (T2DM), focusing on the key mechanisms and pathways involved in insulin metabolism and the development of T2DM and insulin resistance. T2DM is primarily caused by defective insulin secretion by pancreatic β-cells and insulin resistance in insulin-sensitive tissues. Insulin is synthesized in β-cells, stored in granules, and released in response to high glucose levels. The process involves glucose uptake, ATP production, and the opening of voltage-dependent calcium channels, leading to insulin exocytosis. However, factors such as hyperglycemia, hyperlipidemia, and oxidative stress can impair β-cell function, leading to reduced insulin secretion and increased insulin resistance. Insulin resistance is a major contributor to T2DM, affecting tissues such as skeletal muscle, adipose tissue, and the liver. In skeletal muscle, insulin resistance is associated with impaired glucose uptake and glycogen synthesis, often due to defects in insulin signaling pathways. In adipose tissue, insulin resistance leads to increased lipolysis and fatty acid release, contributing to systemic insulin resistance. In the liver, insulin resistance impairs glucose metabolism, leading to increased hepatic glucose production. T2DM is also associated with metabolic memory, where even after glycemic control, complications persist. This is linked to epigenetic changes, oxidative stress, and chronic inflammation. Additionally, mitochondrial dysfunction plays a significant role in T2DM pathogenesis, with impaired mitochondrial biogenesis and increased ROS production contributing to insulin resistance and β-cell dysfunction. Other factors contributing to T2DM include obesity, sedentary lifestyle, and gut dysbiosis. These factors promote chronic inflammation, oxidative stress, and metabolic disturbances that exacerbate insulin resistance and T2DM. The review highlights the complex interplay between genetic, metabolic, and environmental factors in the development of T2DM and its complications, emphasizing the need for a multifaceted approach to its management.This review discusses the pathophysiology of Type 2 Diabetes Mellitus (T2DM), focusing on the key mechanisms and pathways involved in insulin metabolism and the development of T2DM and insulin resistance. T2DM is primarily caused by defective insulin secretion by pancreatic β-cells and insulin resistance in insulin-sensitive tissues. Insulin is synthesized in β-cells, stored in granules, and released in response to high glucose levels. The process involves glucose uptake, ATP production, and the opening of voltage-dependent calcium channels, leading to insulin exocytosis. However, factors such as hyperglycemia, hyperlipidemia, and oxidative stress can impair β-cell function, leading to reduced insulin secretion and increased insulin resistance. Insulin resistance is a major contributor to T2DM, affecting tissues such as skeletal muscle, adipose tissue, and the liver. In skeletal muscle, insulin resistance is associated with impaired glucose uptake and glycogen synthesis, often due to defects in insulin signaling pathways. In adipose tissue, insulin resistance leads to increased lipolysis and fatty acid release, contributing to systemic insulin resistance. In the liver, insulin resistance impairs glucose metabolism, leading to increased hepatic glucose production. T2DM is also associated with metabolic memory, where even after glycemic control, complications persist. This is linked to epigenetic changes, oxidative stress, and chronic inflammation. Additionally, mitochondrial dysfunction plays a significant role in T2DM pathogenesis, with impaired mitochondrial biogenesis and increased ROS production contributing to insulin resistance and β-cell dysfunction. Other factors contributing to T2DM include obesity, sedentary lifestyle, and gut dysbiosis. These factors promote chronic inflammation, oxidative stress, and metabolic disturbances that exacerbate insulin resistance and T2DM. The review highlights the complex interplay between genetic, metabolic, and environmental factors in the development of T2DM and its complications, emphasizing the need for a multifaceted approach to its management.