This review article explores the relationship between diabetes mellitus and oxidative stress. It begins by explaining the role of free radicals (ROS/RNS) in cellular oxidation and the body's antioxidant systems, which help maintain homeostasis. Imbalance between ROS/RNS and antioxidants leads to oxidative stress, a condition associated with various pathological conditions, including diabetes. The article discusses the pathophysiology of diabetes, distinguishing between Type I (insulin-dependent) and Type II (non-insulin dependent) diabetes, and their respective mechanisms of disease development. It highlights the complications of diabetes, such as macrovascular and microvascular issues, and the role of oxidative stress in these complications. The article also delves into the biological roles of free radicals, their production, and scavenging mechanisms. It emphasizes the importance of antioxidants in neutralizing free radicals and preventing oxidative damage. The review further examines the oxidative stress in diabetes, its impact on insulin action, and the biomarkers of oxidative stress, including proteins, lipids, vitamins, glutathione, catalase, and superoxide dismutase. Finally, it concludes by summarizing the evidence linking oxidative stress to diabetes and its complications, suggesting that antioxidants may be a promising therapeutic approach for managing diabetes.This review article explores the relationship between diabetes mellitus and oxidative stress. It begins by explaining the role of free radicals (ROS/RNS) in cellular oxidation and the body's antioxidant systems, which help maintain homeostasis. Imbalance between ROS/RNS and antioxidants leads to oxidative stress, a condition associated with various pathological conditions, including diabetes. The article discusses the pathophysiology of diabetes, distinguishing between Type I (insulin-dependent) and Type II (non-insulin dependent) diabetes, and their respective mechanisms of disease development. It highlights the complications of diabetes, such as macrovascular and microvascular issues, and the role of oxidative stress in these complications. The article also delves into the biological roles of free radicals, their production, and scavenging mechanisms. It emphasizes the importance of antioxidants in neutralizing free radicals and preventing oxidative damage. The review further examines the oxidative stress in diabetes, its impact on insulin action, and the biomarkers of oxidative stress, including proteins, lipids, vitamins, glutathione, catalase, and superoxide dismutase. Finally, it concludes by summarizing the evidence linking oxidative stress to diabetes and its complications, suggesting that antioxidants may be a promising therapeutic approach for managing diabetes.