INS and Hypoglycemia: Failure to test for antibodies could confuse such an approach because insulin-binding autoantibodies (IAA) of the insulin autoimmune syndrome (IAS), when present, could cause hypoglycaemia as well as distort insulin and/or C-peptide results, mimicking and masquerading as other pathologies and factitious hypoglycaemia.1, 2, 3, 4 Test for antibodies (all classes and subclasses) by polyethylene glycol (PEG) is simple, quick and informative, with trivial cost.