The effects of hypoglycaemia on cognitive function will be assessed by repeated measures analysis of variance, with experimental condition as a within-subjects factor, and order of session (euglycaemia-hypoglycaemia or hypoglycaemia-euglycaemia) as a between-subjects factor. This means that performance on cognitive tests will be compared for each patient between their hypoglycaemia and euglycaemia study sessions. Statistical analysis will be performed using SPSS (Statistical Package for the Social Sciences). A p value of less that 0.05 will be considered significant.