Highlights A persistent glycosuria alongside hypoglycemia in pediatric type 1 diabetes mellitus needs further evaluation. Morning hypoglycemia is a limiting side effect of sodium glucose transporter 2 (SGLT2) inhibitors in children younger than 5 years old. SLC5A2 mutation functioning as a SGLT2 inhibitor can result in acceptable range of glycated hemoglobin in younger children and lower required doses of insulin.