Objective-To assess the risk of hyperglycaemia with two standard oral rehydration solutions that contain carbohydrate compared with a carbohydrate free solution during rehydration of diabetic patients with acute diarrhoea. Design-Prospective randomised allocation to one of three oral rehydration solutions (World Health Organisation (glucose), rice, or glycine) groups after admission to hospital with acute diarrhoea. Setting-Dhaka hospital of the International Centre for Diarrhoeal Disease Research, Bangladesh. Subjects-45 diabetic patients aged between 15 and 60 who had had diarrhoea for fewer than three days on admission. Main outcome measures-Fluctuation of blood glucose concentrations measured three times a day, daily stool output, and time taken for recovery from diarrhoea. Results-There were no significant differences in blood glucose concentrations, stool output, and duration of recovery from diarrhoea among the three groups. Conclusions-Oral rehydration solutions containing glucose, rice powder, or glycine can be safely administered to diabetic patients with acute diarrhoea and some dehydration.