Because glucagon increases the level of blood sugar by breaking down fat, protein and amino acids. This leads to anemia, diarrhea and rapid weight loss. An associated paraneoplastic syndrome, necrolytic migratory erythema, causes widespread blisters and edema. Patients usually develop the symptoms of diabetes mellitus, although the etiology is different. The disease is usually diagnosed by the presence of very high levels of glucagon in the blood, but many patients show only elevated levels.