The patients with CPT-I deficiency show hypoketotic hypoglycemia during infancy and are detected by newborn screening using tandem mass spectrometer (MS/MS) with a screening marker of the ratio of free carnitine to long-chain acylcarnitines and such confirmation tests as enzyme assay or gene analysis are necessary. This evidence concerns the gene CPT1A and hyperinsulinemic hypoglycemia, familial, 4.