A supervised fast was performed and the test was stopped after 28 h due to symptoms of confusion and disorientation, with a glucose level of 1.3 mmol/L, insulin levels of 46.48 mU/L (reference range 2.6–24.9 mU/L), and C-peptide of 1.21 nmol/L (reference range 0.27–1.27), confirming endogenous hyperinsulinemic hypoglycemia. This evidence concerns the gene INS and hyperinsulinemic hypoglycemia.