Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzymopathy and hemolytic anemia can be triggered by many drugs, by the ingestion of fava beans, and by metabolic imbalances. Nonetheless, only sporadic reports of hemolytic anemia due to G6PD deficiency in patients with type 1 diabetes mellitus (DM1) have been reported to date. We describe an 8 year-old Sicilian boy who suffered from hemolytic anemia some days after admission for DM1. On admission, acid-base equilibrium was normal but 4 days later he presented hemolytic anemia with G6PD deficiency, confirmed by personal and family history and laboratory evaluation. We suggest that the hemolytic crisis in this patient was triggered by the relative hypoglycemia that followed insulin administration. The interference of acidosis, infections, drugs, food or other triggering agents was excluded. This report demonstrates that hemolysis may represent a possible complication of DM treatment in patients with G6PD deficiency and we recommend careful clinical surveillance in these patients.