Figure.

Hypoglycemia diagnosis based on plasma metabolic fuel responses. Measurement of major fuels (lactate as a gluconeogenic substrate, FFA from adipose tissue lipolysis, and beta-hydroxybutyrate as the major ketone from hepatic ketogenesis) at a time of hypoglycemia segregates four major groups of disorder: gluconeogenesis defects, ketotic hypoglycemia disorders, fatty acid oxidation defects, and hyperinsulinism or its mimickers. Supplemental tests can be added to support the diagnosis (eg, plasma acyl-carnitine profile, glucagon stimulation test). Abbreviations: FFA (free fatty acids), GH (growth hormone).