We have assessed whether glucose concentration and patient outcome are related in hospitalised patients when glycaemia is quantified in detail. Continuous glucose monitoring was performed on 47 consecutive subjects with an acute exacerbation of chronic obstructive pulmonary disease. Length of hospital stay increased by 10% for each mmol/L increase in mean glucose (P=0.01). In a multivariable analysis, mean glucose was independently associated with length of hospital stay (P=0.02). These data add weight to evidence that hyperglycaemia may adversely affect patient outcomes in hospitalised patients.