Diabetes is one of the most common metabolic diseases, which affects more than 400 million people worldwide. Numerous research groups are working on elucidating mechanisms underlying the pathogenesis of diabetes. For several decades, β-cells and insulin were at the center of interest in the field; however, this paradigm has changed with new data, showing the importance of α-cells in the aetiology of diabetes. Glucagon, secreted in these cells, plays a crucial role in the regulation of glucose homeostasis. Recently, it has been argued that impaired insulin signaling might not have the strongest impact on metabolic homeostasis, while glucagon could be the main driver of the disease. However, the data about glucagon dynamics and its role in diabetes remain scarce. In the present study, we analyzed changes in plasma/total pancreatic glucagon, α- and β-cell proliferation, plasma leptin, using a murine model of graded β-cell loss.