AbstractHypoglycaemia unawareness can be a devastating complication in both types of diabetes. It is probably becoming more common as patients are urged to tighten their glycaemic control. The effects of improving glycaemic control on the background of increasing duration of diabetes are the main known risk factors for the condition. Antecedent hypoglycaemia diminishes physiological responses, and impairs the ability to identify further episodes, leading to a vicious downwards spiral and a high risk of further severe hypoglycaemic episodes. Fully established hypoglycaemia unawareness is thankfully rare, but difficulty in recognising the onset of hypoglycaemia is common. Therefore effective treatments to reverse or prevent hypoglycaemia unawareness are urgently needed.This review article examines the evidence around the pathophysiology of hypoglycaemia unawareness, and current therapeutic strategies. Copyright © 2011 John Wiley & Sons.