Insulinoma is a rare diagnosis in the general population with estimates of 1 in 250,000 people per year. Reports of these pancreatic islet cell tumors are even more unusual in children and adolescents. Chronic hypoglycemia due to an insulinoma often presents with neuroglycopenic symptoms that can easily be overlooked, especially in adolescents where nonspecific complaints are common. This may result in delayed diagnosis with prolonged periods of untreated hypoglycemia and associated complications. The rarity of pediatric insulinoma, vagueness of presenting symptoms, and challenge of tumor localization make insulinoma a true diagnostic quandary for clinicians. In this report, we present a 15-year-old female who visited her primary care provider complaining of intermittent episodes of altered mental status including fatigue, irritability, and poor concentration. Her outpatient management included routine laboratory studies, drug screening, electroencephalogram (EEG), valproic acid initiation, CT scan of the abdomen, and endoscopic ultrasound with documentation of hypoglycemia, but otherwise inconclusive results. The patient was admitted to a tertiary children’s hospital with severe refractory hypoglycemia 8 months after the initial evaluation. A serum critical sample was obtained and magnetic resonance imaging (MRI) of the abdomen performed which confirmed the presence of a pancreatic mass ultimately identified as an insulinoma. She went on to have surgical resection of her tumor resulting in complete resolution of her hypoglycemia and associated symptoms. Within this report we demonstrate the importance of being vigilant for fasting hypoglycemia secondary to insulinoma even when the patient presents with nonspecific symptoms such as fatigue, irritability, or problems with concentration. If these neuroglycopenic complaints are unnoticed or misdiagnosed, patients with a potentially curable disease are put at risk of neurologic injury, or even death, due to untreated severe hypoglycemia.