What's a somogyi effect ?

Somogyi effect is a phenomenon observed in diabetic patients who are treated with an insulin regimen involving the evening dose. Due to high dose of insulin in the evening there is nocturnal hypoglycaemia which is responded by counter-regulatory harmones lile cortisol, adrenaline and other stress hormones to elevate the blood sugar. therefore despite high insulin dose and nocturnal (1 am) hypoglycaemia, there is fasting hyperglycaemia induced by the counter-regulatory hormones, The strategy should by to take a midnight RBS sample and if hypoglyemia is found, the evening dose of insulin should be reduced .  

If diabetic patient received his insulin at sleep time without eating, he will undergo early morning hypoglycemia during sleep, anti-insulin hormones will released in response to hypoglycemia, it may reverse the condition to hyperglycemia through their actions on body metabolism.

In the1930s, Dr Michael Somogyi speculated that hypoglycemia during the late evening induced by insulin could cause a counter regulatory hormone response (see the image below) that produces hyperglycemia in the early morning.

Ref:

Somogyi Phenomenon 

• Author: Michael Cooperman, MD; Medscape

In diabetes, the occurrence of reactive hyperglycemia following hypoglycemia. Also called posthypoglycemic hyperglycemia, Somogyi phenomenon

well this is also know as somogyi phenomenon in diabetic patients. when the blood sugar lever goes very down(hypoglycemia) in that response the body reacts and cause high blood sugar(hyperglycemia). in medical languge when the blood sugar goes down stress hormone named cortisole released which further pushed glucagon occurrance which ultimately causes hyperglycemia.