2020 Nov 21. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan–.
Hypoglycemia is often defined by a plasma glucose concentration below 70 mg/dL; however, signs and symptoms may not occur until plasma glucose concentrations drop below 55 mg/dL. The symptoms of Whipple's triad have been used to describe hypoglycemia since 1938. For Whipple's triad, the practitioner must first recognize symptoms of hypoglycemia, then obtain low blood glucose, and finally, demonstrate immediate relief of symptoms by the correction of the low blood glucose. Glucose is the primary metabolic fuel for the brain under physiologic conditions. Unlike other tissues of the body, the brain is very limited in supplying its glucose. Expectedly, the brain requires a steady supply of arterial glucose for adequate metabolic function. Potential complications can arise from an interruption in the glucose supply. As such, protective mechanisms to guard against low serum blood glucose (hypoglycemia) have evolved in the body.
During fasting states, serum glucose levels are maintained via gluconeogenesis and glycogenolysis in the liver. Gluconeogenesis is the pathway in which glucose is generated from non-carbohydrate sources. These non-carbohydrate sources could be protein, lipids, pyruvate or lactate. In contrast, glycogenolysis is the breakdown of glycogen into glucose product. Much of glycogenolysis occurs in hepatocytes (liver) and myocytes (muscle).
Hypoglycemia is most often seen in patients suffering from diabetes who are undergoing pharmacologic intervention. Amongst this group, patients with type 1 diabetes are 3 times as likely to experience hypoglycemia as compared to patients with type 2 diabetes when receiving treatment.