AbstractAimClinical trials showed the efficacy of sodium‐glucose cotransporter 2 inhibitors for type 1 diabetes (T1D) by significant reductions in body weight and glycaemic variability, but elevated susceptibility to ketoacidosis via elevated glucagon secretion was a potential concern. The Suglat‐AID evaluated glucagon responses and its associations with glycaemic control and ketogenesis before and after T1D treatment with the sodium‐glucose cotransporter 2 inhibitor, ipragliflozin.MethodsAdults with T1D (n = 25) took 50‐mg open‐labelled ipragliflozin daily as adjunctive to insulin. Laboratory/clinical data including continuous glucose monitoring were collected until 12 weeks after the ipragliflozin initiation. The participants underwent a mixed‐meal tolerance test (MMTT) twice [before (first MMTT) and 12 weeks after ipragliflozin treatment (second MMTT)] to evaluate responses of glucose, C‐peptide, glucagon and β‐hydroxybutyrate.ResultsThe area under the curve from fasting (0 min) to 120 min (AUC_0‐120min) of glucagon in second MMTT were significantly increased by 14% versus first MMTT. The fasting and postprandial β‐hydroxybutyrate levels were significantly elevated in second MMTT versus first MMTT. The positive correlation between postprandial glucagon secretion and glucose excursions observed in first MMTT disappeared in second MMTT, but a negative correlation between fasting glucagon and time below range (glucose, <3.9 mmol/L) appeared in second MMTT. The percentage changes in glucagon levels (fasting and AUC_0‐120min) from baseline to 12 weeks were significantly correlated with those in β‐hydroxybutyrate levels.ConclusionsIpragliflozin treatment for T1D increased postprandial glucagon secretion, which did not exacerbate postprandial hyperglycaemia but might protect against hypoglycaemia, leading to reduced glycaemic variability. The increased glucagon secretion might accelerate ketogenesis when adequate insulin is not supplied.