The present invention is directed to a method of detecting persistent hyperinsulinemic hypoglycemia of infancy comprising obtaining a sample comprising patient nucleic acids from a patient tissue sample; amplifying sulfonylurea receptor specific nucleic acids from said patient nucleic acids to produce a test fragment; obtaining a sample comprising control nucleic acids from a control tissue sample; amplifying control nucleic acids encoding wild type sulfonylurea receptor to produce a control fragment; comparing the test fragment with the control fragment to detect the presence of a sequence difference in the test fragment, wherein a difference in said test fragment indicates persistent hyperinsulinemic hypoglycemia of infancy. A diagnostic kit and primers for the detection of persistent hyperinsulinemic hypoglycemia of infancy are also within the scope of the present invention.