Hypoglycemia (hypoglycaemia in the UK) is a medical term referring to a pathologic state produced by a lower than normal amount of sugar (glucose) in the blood. The term hypoglycemia literally means "low blood sugar". Hypoglycemia can produce a variety of symptoms and effects but the principal problems arise from an inadequate supply of glucose as fuel to the brain, resulting in impairment of function (neuroglycopenia). Derangements of function can range from vaguely "feeling bad" to coma and (rarely) death. Hypoglycemia can arise from many causes, and can occur at any age. The most common forms of moderate and severe hypoglycemia occur as a complication of treatment of diabetes mellitus with insulin or oral medications.
Although 70 mg/dl (3.9 mmol/l) is commonly cited as the lower limit of normal glucose, different values may be defined as low for different populations, purposes, or circumstances. The precise level of glucose considered low enough to define hypoglycemia is dependent on (1) the measurement method, (2) the age of the person, (3) presence or absence of effects, and (4) the purpose of the definition. This article expresses glucose in milligrams per deciliter (mg/dl or mg/100 ml) as is customary in the United States, while millimoles per liter (mmol/l or mM) are the SI (International System) units used in most of the rest of the world. Values in mg/dl can be converted to mmol/l by dividing by 18 (e.g., 90 mg/dl = 5 mmol/l or 5 mM).
Management of hypoglycemia involves immediately raising the blood sugar to normal, determining the cause, and taking measures to prevent future episodes. The blood glucose can be raised to normal within minutes by taking (or receiving) 10-20 grams of carbohydrate. It can be taken as food or drink if the person is conscious and able to swallow. This amount of carbohydrate is contained in about 3-4 ounces (100-120 ml) of orange, apple, or grape juice, about 4-5 ounces (120-150 ml) of regular (non-diet) soda), about one slice of bread, about 4 crackers, or about 1 serving of most starchy foods. Starch is quickly digested to glucose, but adding fat or protein retards digestion. Symptoms should begin to improve within 5 minutes, though full recovery may take 10-20 minutes. Overfeeding does not speed recovery and if the person has diabetes will simply produce hyperglycemia afterwards.
If a person is suffering such severe effects of hypoglycemia that they cannot (due to combativeness) or should not (due to seizures or unconsciousness) be given anything by mouth, glucose can be given by intravenous infusion or the glucose can be rapidly raised by an injection of glucagon. Further details of glucagon use are provided in the article on diabetic hypoglycemia.