It is widely accepted that alcohol consumption by patients with insulin-dependent (Type 1) diabetes mellitus is associated with an increased risk of hypoglycaemia. This association has been the subject of few studies, however, and there is not much evidence to support advice currently given to patients. Available information suggests that moderate alcohol consumption by healthy, fed subjects does not cause acute hyper- or hypoglycaemia although there may be a delayed risk of hypoglycaemia the morning after evening alcohol intake. Alcohol can lead to potentially hazardous hypoglycaemia in fasted individuals or in those dependent upon alcohol and has been associated with hypoglycaemic unawareness.