INS and type 1 diabetes mellitus: The key pathophysiological abnormality is a blunted counter-regulatory response to hypoglycaemia.3 The prevalence of IAH has been estimated to be 27% in pwT1D and 14% in people with type 2 diabetes (T2D),4 although there is some evidence that the prevalence is decreasing.5,6 Under physiological conditions, the first line of defence against low blood glucose is inhibition of insulin secretion as glucose levels fall, but this is absent in type 1 diabetes (T1D) as insulin needs to be given exogenously in the absence of β-cell secretion (Figure 1).