Large dose of insulin injection will cause hypoglycaemia. Hypoglycemia triggers increased secretion of at least four counterregulatory hormones: glucagon, epinephrine, growth hormone, and coisol. Insulin inhibits glucagon secretion, so low blood glucose has an indirect effect on glucagon secretion through removal of inhibition by insulin. Circulating catecholamines stimulate secretion of glucagon b2-adrenergic receptors Even mild hypoglycaemia is sensed by the CNS, which triggers a central sympathetic response. Glucagon and epinephrine increase the hepatic output of glucose by increasing glycogenolysis. The keys to counter-regulation appear to be glucagon>epinephrine Plasma glucose levels at which various effects of hypoglycemia appear :