This was a single site, non-randomized study. The study consisted of a screening visit (Visit 1), during which the subject was consented and the inclusion and exclusion criteria confirmed, an experimental intervention (Visit 2) and a follow-up visit (Visit 3). The experimental intervention was based on an initial glucose clamp involving a basal intravenous (IV) insulin infusion and IV insulin boluses plus IV glucose infusion / IV glucose boluses as required to maintain euglycemic, hypoglycemic and hyperglycemic plateaus respectively in 41 subjects with Type 1 or Type 2 Diabetes. At the end of hour five of the study the glucose clamp was discontinued and subjects given a standardized meal to stimulate a hyperglycemic excursion