For diabetic patients, hypoglycemia is defined as glucose levels less than 4 mmol/L, and for non-diabetic individuals, or healthy people, low blood sugar is characterized by levels less than 2.8 mmol/L. Hypoglycemia initially causes metabolic abnormalities in the brain since brain cells in the middle of the brain can't break down fats or proteins; they can only use the simplest sugars, which is the glucose in our blood, as their energy source.

When the concentration of sugar in the blood decreases, the brain cells fail to absorb enough energy, which can lead to abnormalities in brain function, resulting in symptoms like fatigue and drowsiness. If glucose is not consumed at this point, the further deficiency in energy for brain cells may lead to coma, making hypoglycemia a very dangerous condition.