There are hundreds of causes of hypoglycemia. Normally, the defensive, physiological response to a falling blood glucose is reduction of insulin secretion to undetectable levels, and release of glucagon, adrenaline, and other counterregulatory hormones. This shift of hormones initiates glycogenolysis and gluconeogenesis in the liver, and lipolysis in adipose tissue. Lipids are metabolized to triglycerides, in turn to fatty acids, which are transformed in the mitochondria of liver and kidney cells to the ketone bodies— acetoacetate, beta-hydroxybutyrate, and acetone. Ketones can be used by the brain as an alternate fuel when glucose is scarce. A high level of ketones in the blood, ketosis, is thus a normal response to hypoglycemia in healthy people of all ages. The presence or absence of ketosis is therefore an important clue to the cause of hypoglycemia in an individual patient. Absence of ketosis ("nonketotic hypoglycemia") most often indicates excessive insulin as the cause of the hypoglycemia. Less commonly, it may indicate a fatty acid oxidation disorder.
Ketotic hypoglycemia
Reactive hypoglycemia
Hyperinsulinemic hypoglycemia
Diabetic hypoglycemia
Idiopathic hypoglycemia
Stress hyperglycemia
Hyperproinsulinemia
Ketosis-prone diabetes