Abstract Disclosure: R.E. Thomas: None. A. Charales: None. B. Bangash: None. S. Haider: None. S. Ouais: None. Introduction: Non-insulinoma pancreatogenous hypoglycemia syndrome (NIPHS) is a rare condition characterized by endogenous hyperinsulinemic hypoglycemia after meals. This article explores NIPHS, emphasizing its occurrence post-gastric sleeve surgery. We delve into clinical features, diagnosis, treatment, and challenges, using a case presentation to illustrate complexities.Clinical Features and Classification:NIPHS entails endogenous hyperinsulinemic hypoglycemia without islet cell neoplasms, featuring islet cell hypertrophy. Formerly "Nesidioblastosis," post-RYGB cases constitute a distinct diagnosis. Common features include postprandial hyperinsulinemic hypoglycemia, negative radiologic localization, and a positive calcium stimulation test.Patients present postprandial hypoglycemia 2-4 hours after meals, with symptoms like tachycardia, tremors, confusion, and occasional seizures. Lab findings include elevated insulin, C peptide, and pro-insulin, low beta-hydroxybutyrate, and negative sulfonylurea/meglitinide screen.Diagnostic Workup:Evaluate glucose, insulin, pro-insulin, C peptide, beta-hydroxybutyrate, and sulfonylurea/meglitinide. Ultrasound differentiates insulinoma from diffuse processes. If negative, conduct SACST for localization.Case Presentation:A 37-year-old female post-gastric sleeve surgery presented with severe hypoglycemia. Symptoms included confusion, nausea, and palpitations, occurring postprandially, relieved by food or juice. Glucagon was administered, and consultations sought. Diazoxide stabilized blood glucose.Treatment Modalities:Dietary modifications reduce free carbohydrate intake, spaced meals minimize hyperinsulinemic episodes. Medical management (octreotide, verapamil, diazoxide, acarbose) proves effective, especially post-gastric bypass. Sub-total pancreatectomy is considered in severe refractory cases.Multidisciplinary Approach:Management involves endocrinologists, surgeons, radiologists, and dietitians. Regular monitoring assesses efficacy, adjusts medications, and addresses complications. Challenges and Future Perspectives: NIPHS complexities include variable presentation and diagnostic challenges. Research should refine criteria, explore interventions, and understand pathophysiology. Conclusion: Non-insulinoma pancreatogenous hypoglycemia syndrome, especially post-gastric sleeve surgery, presents complexities. This exploration highlights clinical aspects, diagnostics, and management challenges, emphasizing the need for a multidisciplinary approach. Continued research aims to enhance diagnostic precision and improve outcomes for those affected by this intriguing syndrome. Presentation: 6/3/2024