INS and Hypoglycemia: Importantly, evidence of Whipple's triad (documentation of hypoglycemia in the presence of clinical symptoms with improvement after ingestion of carbohydrates (Whipple & Elliott 1938)) is mandatory in order to pursue to the standardized provocation test, i.e. a 72-h fasting test with monitoring of glucose, insulin and C-peptide levels (Grant 2005).