This article reviews the prevalence and molecular genetics of diabetes mellitus, emphasizing its global epidemic status. The Western Pacific region has the highest diagnosed diabetes prevalence (37.5%), while the Middle East and North Africa have the highest adult incidence (10.9%). The article discusses various types of diabetes, including type 1, type 2, and gestational diabetes, highlighting their classification, etiology, and genetics. Type 1 diabetes, often autoimmune, affects 5-10% of diabetics and is characterized by the autoimmune destruction of pancreatic beta cells. Type 2 diabetes, the most common form, is influenced by genetic and environmental factors. The article also covers monogenic diabetes, exocrine pancreas diseases, and complications related to diabetes, such as nephropathy, retinopathy, and cardiovascular issues. It emphasizes the importance of early detection and diagnosis using tools like HbA1c, which has been recommended by multiple expert committees. The molecular genetics of diabetes complications, including specific gene mutations and polymorphisms, are discussed, along with their impact on disease progression and management. The conclusion underscores the need for further research to improve diagnosis, treatment, and genetic counseling, and to reduce the burden of chronic complications associated with diabetes.This article reviews the prevalence and molecular genetics of diabetes mellitus, emphasizing its global epidemic status. The Western Pacific region has the highest diagnosed diabetes prevalence (37.5%), while the Middle East and North Africa have the highest adult incidence (10.9%). The article discusses various types of diabetes, including type 1, type 2, and gestational diabetes, highlighting their classification, etiology, and genetics. Type 1 diabetes, often autoimmune, affects 5-10% of diabetics and is characterized by the autoimmune destruction of pancreatic beta cells. Type 2 diabetes, the most common form, is influenced by genetic and environmental factors. The article also covers monogenic diabetes, exocrine pancreas diseases, and complications related to diabetes, such as nephropathy, retinopathy, and cardiovascular issues. It emphasizes the importance of early detection and diagnosis using tools like HbA1c, which has been recommended by multiple expert committees. The molecular genetics of diabetes complications, including specific gene mutations and polymorphisms, are discussed, along with their impact on disease progression and management. The conclusion underscores the need for further research to improve diagnosis, treatment, and genetic counseling, and to reduce the burden of chronic complications associated with diabetes.