Fasting during Ramadan is a major tenet of the Muslim religion. All adults after the age of puberty are required to do so if health permits. However, there are exemptions to this requirement and having a chronic condition such as diabetes is one. Nevertheless, many adults and adolescents feel obliged to fast during Ramadan even though there is no absolute need to do so. This obligation must be respected. There are few data to support this practice in those whose condition, such as diabetes, potentially makes them vulnerable to developing problems during prolonged fasting. This study was designed to examine the ability and safety of young people with diabetes to be able to fast if they so desire. Two groups of patients were studied, those on a multiple injection, so-called basal-bolus, regimen and those on a 'conventional' twice daily pre-mixed insulin regimen. All patients showed a tendency to high blood glucose at the time of commencing their fast. Those on twice daily insulin continued to have hyperglycaemia during the day whilst those on basal-bolus insulin showed a steady fall in blood glucose towards normal by the time of breaking their fast. Although there was a greater tendency to hypoglycaemia in the basal-bolus group, this could be successfully prevented by reducing the dose of basal insulin by 10-20%. We recommend that it is safe for adolescents with diabetes to fast during Ramadan as long as they reduce their basal insulin by this amount and continue to monitor their blood glucose regularly.