Diabetes mellitus (DM) is a globally prevalent metabolic disorder affecting both pediatric and adult populations, characterized by chronic hyperglycaemia due to impaired insulin secretion, insulin resistance, or both. The rising incidence of both Type 1 Diabetes Mellitus (T1DM) in children and adolescents, and Type 2 Diabetes Mellitus (T2DM) in youth and adults, reflects complex interactions between genetic, immunological, environmental, and lifestyle factors. This review highlights recent advances in the diagnosis and management of diabetes across the lifespan, with a specific focus on pharmacological strategies particularly insulin therapy and dietary interventions. In pediatric T1DM, innovations in insulin delivery systems, including continuous subcutaneous insulin infusion and hybrid closed-loop technologies, have improved glycaemic control and quality of life. Meanwhile, in both youth-onset and adult T2DM, early and aggressive interventions integrating lifestyle changes, oral antidiabetic agents (e.g., metformin, SGLT2 inhibitors, GLP-1 receptor agonists), and timely insulin initiation are essential for mitigating complications. Dietary modifications and structured physical activity remain foundational to diabetes prevention and treatment, offering cardio metabolic benefits that transcend glycaemic regulation. The review also explores the growing role of continuous glucose monitoring, automated insulin delivery, and emerging drug delivery platforms in transforming diabetes care. Special attention is given to psychosocial factors, the transitional challenges from pediatric to adult care, and future directions in immunotherapy, stem cell research, and nanotechnology-based therapeutics. Together, these advances underscore the shift toward precision, technology-enabled, and patient-centered diabetes management across all age groups.