This is a Phase 2, multi-center, randomized, placebo-controlled, double-blind parallel group study with open-label follow-up designed to evaluate the efficacy of CSI-Glucagon™ for the prevention of hypoglycemia with lower IV glucose infusion rates when delivered subcutaneously to patients up to 1 year of age with congenital hyperinsulinism. CSI-Glucagon™ is expected to provide a better inpatient treatment option compared to the current standard of care.