Abstract Disclosure: K. Kim: None. E. Mun: None. C. Jung Eun: None. R. Lee: None. K. Hae Soon: None. A Case of Continuous Glucose Monitoring in Children with Glutamate Dehydrogenase(GLUD1) Hyperinsulinism Background: Continuous glucose monitoring (CGM) is increasingly being used in pediatric patients with diabetes. CGM can help prevent hypoglycemia and support the management of hypoglycemic problems. Congenital hyperinsulinism is a rare condition in which hypoglycemia occurs due to hyperinsulinemia caused by the dysregulation of insulin secretion, and it can lead to complications such as developmental delay and seizures. Case presentation: A 14 months years old, male infant was referred to the pediatric emergency room representing symptoms of GTC type seizure during 2-3 minutes and hypoglycemia. He had no perinatal problems with no significant family history. During seizure, He was found to have a blood glucose of 39mg/dL, ammonia of 183μmol/L, insulin of 28.3 mcg/mL and ketone 203.4μmol/L. C-peptide was 1.4 ng/mL (≥ 0.5ng/mL) and free fatty acid was 0.492mmol/L (<1.7mmol/L) for evaluation. He was thought to have GDH hyperinsulinism. Blood glucose level was followed up with feeding frequency and protein restricted diet. Congenital hyperinsulinism genetic test was requested. Brain CT showed normal. EEG revealed no focal abnormalities, no persistent asymmetries. CGM was used in patient. Diazoxide was started with 5mg/kg/day in 2 divided doses and then blood glucose level was observed below 60mg/dL 3-4 times for day. Complete blood counts and uric acid levels were measured at baseline and 5 days after starting diazoxide therapy, and thereafter increase to 6.25mg/kg/day Conclusions: In children with GDH hyperinsulinism, the utilization of CGM can serve as a tool to assess the impact of treatment before and after medication therapy, as well as also aiding in hypoglycemia prevention. Presentation: 6/2/2024