Type 2 diabetes is a very common metabolic disorder worldwide. The main defects of this disease are insulin resistance and a β cell dysfunction, leading to a reduction of insulin secretion over time. Insulin secretion is a complex mechanism that involves interactions among all the cells of the pancreatic insula. In addition, glucolipotoxicity may affect reversibly insulin secretion in type 2 diabetes. In recent years, several novel treatments have been becoming available for type 2 diabetes, nevertheless insulin still maintains an important role overall in specific situations including severe metabolic decompensation or pregnancy. The aim of the present narrative review is to discuss the main indications of insulin in the treatment of type 2 diabetes.