2022 Jan 4. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 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 with glucose treatment. 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 stored into glucose products. Much of glycogenolysis occurs in hepatocytes (liver) and myocytes (muscle).
Hypoglycemia is most often seen in patients who have diabetes that undergoing pharmacologic intervention. Among this group, patients with type 1 diabetes are three times as likely to experience hypoglycemia than patients with type 2 diabetes when receiving treatment.