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(Low Blood Sugar)

Hypoglycemia Overview

Hypoglycemia (low blood sugar) is a commonly perceived problem. In actuality, while some or many of the symptoms may be present, it is rarely confirmed or documented. The presence of true, documented hypoglycemia in the absence of diabetes treatment must be evaluated comprehensively by an endocrinologist. Hypoglycemia most often affects those at the extremes of age, such as infants and the elderly, but may happen at any age. Generally, hypoglycemia is defined as a serum glucose level (the amount of sugar or glucose in your blood) below 70 mg/dL.

As a medical problem, hypoglycemia is diagnosed by the presence of three key features (known as Whipple's triad). Whipple's triad is:

  1. symptoms consistent with hypoglycemia,
  2. a low plasma glucose concentration, and
  3. relief of symptoms after the plasma glucose level is raised.

Symptoms of hypoglycemia typically appear at levels below 60 mg/dL. Some people may feel symptoms above this level. Levels below 50 mg/dL affect brain function.

The body regulates its glucose level—the primary source of energy for the brain, muscles, and other essential cells - by the actions of different hormones. These hormones include insulin (which lowers the blood sugar level) and other chemicals which raise blood sugar (such as glucagon, growth hormone, and epinephrine).

  • Both insulin and glucagon are manufactured in the pancreas, an organ near the stomach which assists the digestive tract. Special cells in the pancreas, called beta cells, make insulin. Alpha cells in the pancreas make glucagon.
  • The role of insulin is to help in the absorption of glucose from the blood by causing it to be stored in the liver or be transported into other tissues of the body (for metabolism or storage).
  • Glucagon increases the amount of glucose in the blood by breaking down stored glucose (starch, called glycogen) and releasing it from the liver into the bloodstream.
  • Insulin and glucagon are usually correctly balanced if the liver and pancreas are functioning normally.

Traditionally considered a stress hormone, epinephrine (or adrenalin) is made in the adrenal gland and in certain cells in the central nervous system. Epinephrine also elevates blood glucose levels by making glucose available for the body during a time of stress. When this mechanism is not working properly, hypoglycemia can result. Other hormones also help in raising the level of blood glucose, like cortisol made by the adrenal gland and growth hormone made by the pituitary gland.

Last Reviewed 11/20/2017

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Patient Comments & Reviews

The eMedicineHealth doctors ask about Hypoglycemia (Low Blood Sugar):

Hypoglycemia - Effective Treatments

What kinds of treatments have been effective for your hypoglycemia?

Hypoglycemia - Symptoms

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Hypoglycemia Causes

Common causes of low blood sugar include the following:

  • Overmedication with insulin or antidiabetic pills (for example, sulfonylurea drugs)
  • Use of medications such as beta blockers, pentamidine, and sulfamethoxazole and trimethoprim (Bactrim, Septra)
  • Use of alcohol
  • Missed meals
  • Reactive hypoglycemia is the result of the delayed insulin release after a meal has been absorbed and occurs 4-6 hours after eating.
  • Severe infection
  • Cancer causing poor oral intake or cancer involving the liver
  • Adrenal insufficiency
  • Kidney failure
  • Liver failure
  • Congenital, genetic defects in the regulation of insulin release (congenital hyperinsulinism)
  • Congenital conditions associated with increased insulin release (infant born to a diabetic mother, birth trauma, reduced oxygen delivery during birth, major birth stress, Beckwith-Wiedemann syndrome, and rarer genetic conditions)
  • Insulinoma or insulin-producing tumor
  • Other tumors like hepatoma, mesothelioma, and fibrosarcoma, which may produce insulin-like factors

What follows are expansions on the points noted above and should be incorporated within those points (such as cancer, diabetes drugs, organ failures).

  • Most cases of hypoglycemia in adults happen in people with diabetes mellitus. Diabetes has two forms, type 1 (loss of all insulin production) and type 2 (inadequate insulin production due to resistance to the actions of insulin). People with type 1 diabetes must take insulin to control their glucose level; if they skip meals or have a decreased appetite without changing their insulin dose, they may develop hypoglycemia. Insulin is also used to treat some people with type 2 diabetes.
  • If a person with type 1 diabetes accidentally takes too much insulin, or a person with type 2 diabetes accidentally takes too much of their oral medications or insulin, he or she may develop hypoglycemia. Even when a diabetic patient takes medications correctly, improper meals, odd mealtimes, or excessive exercise may result in hypoglycemia.

Read What Your Physician is Reading on Medscape

Hypoglycemia »

Hypoglycemia is a syndrome characterized by a reduction in plasma glucose concentration to a level that may induce symptoms of low blood sugar.

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