Insulinomas are often difficult to localize. We present a 47-year-old woman who had recurrent neuroglycopenic symptoms and positive Whipple triad for 28 months. The 14 hours of fasting test confirmed the diagnosis of endogenous hyperinsulinemic hypoglycemia which is highly suspicious for the presence of an insulinoma. Previously performed MRI, endoscopic ultrasound, In-pentetreotide SPECT/CT, and Ga-DOTA-exendin-4 PET/CT did not show any evidence of an insulinoma. Subsequently, Ga-DOTA-exendin-4 PET/CT was repeated with the previous infusion of a colloidal volume replacement fluid (Gelofusine), known to reduce Ga-DOTA-exendin-4 accumulation in the kidneys. Consequently, the insulinoma was unmasked from the left kidney, allowing curative surgery.