This book represents a comprehensive exploration of the potential of natural compounds derived from plants and marine sources in the battle against the global epidemic of diabetes. Diabetes mellitus, a complex metabolic disorder, continues to rise in prevalence worldwide, necessitating effective treatments and interventions. This book provides a deep understanding of the multifaceted nature of diabetes mellitus, addressing its diverse forms and the intricate factors contributing to its development. It elucidates the chronic hyperglycemia characteristic of diabetes, arising from deficiencies in insulin secretion, action, or both, and the associated symptoms such as excessive thirst, urinary output, and the presence of ketone bodies in the blood or urine, indicating ketoacidosis. Authored by experts from esteemed institutions, the chapters present in-depth insights into the therapeutic potential of phytoconstituents for managing diabetes. Covering herbal products, Thai traditional herbal remedies, marine-based solutions, and various natural compounds, this book explores their roles in mitigating oxidative stress, inflammation and enhancing insulin sensitivity, all with minimal side effects. With a focus on biological properties, mechanisms of action, and clinical applications, this book is an invaluable resource for researchers, clinicians, and anyone interested in diabetes mellitus. It is an essential contribution to the ongoing efforts to understand, prevent, and treat diabetes and its complications. Ultimately, it aims to improve diabetes care and enhance the well-being of individuals affected by this global health challenge.