INS and Hypoglycemia: The Endocrine Society Clinical Practice Guidelines (ESCPG) define endogenous insulin-mediated hypoglycaemia as a plasma glucose concentration of <55 mg/dl combined with insulin ≥3 μU/ml (18 pmol/L), C-peptide ≥0.6 ng/mL (0.2 nmol/L) and Proinsulin ≥5.0 pmol/L, in association with signs and symptoms attributable to hypoglycaemia [10].