Hypoglycemia is a common and serious medical emergency which may occur in both daibetic and non-diabetic patients. The signs and symptoms of hypoglycaemia may be present in many individuals, but may also be masked in several individuals due to a condition called hypoglycaemia induced autonomic failure. This presentation aims to deal with the causes, clinical features, diagnosis and management of various causes of hypoglycaemia. The causes of hypoglycaemia may be divided into hypoglycaemia in ill or medicated individuals and hypoglycaemia in previously asymptomatic individuals. A variety of causes are discussed under both headings. Management of hypoglycaemia is also discussed in detail. There is also a brief discussion about management of insulinoma.