What condition occurs when glucose in the blood falls below levels necessary for normal and efficient brain functioning?

The condition that occurs when glucose in the blood falls below levels necessary for normal and efficient brain functioning is called hypoglycemia. It is characterized by a significant drop in blood glucose levels, usually below 70 mg/dL (milligrams per deciliter). Hypoglycemia can manifest in individuals with certain medical conditions, such as diabetes, and in response to certain medications, especially those used to treat diabetes.