Hypoglycemia (hy-po-gly-SEE-mee-uh) is a condition that occurs when the amount of sugar in the blood gets too low, also called low blood sugar.

Melinda's Story

Melinda was at the mall with friends when she started to feel weak and uncoordinated. She developed a pounding headache, began to shake and sweat, and could not see very well. Because Melinda has diabetes * * if not treated. After eating her candy bar, Melinda felt better within minutes.

What Is Hypoglycemia?

Hypoglycemia is a common medical emergency and means low (hypo) blood sugar (glycemia). Hypoglycemia is not a disease; it is a symptom of a problem the body has with regulating blood sugar. Its opposite, hyperglycemia (hy-per-gly-SEE-mee-uh), means too much sugar in the blood, which is one of the features of diabetes.

Glucose is a sugar that represents an important source of energy for the body. The main dietary sources of glucose are carbohydrates found in foods such as rice, potatoes, bread, tortillas, cereal, milk, fruit, and sweets. After a meal, digestion breaks down food, and glucose molecules are absorbed into the bloodstream and carried to the cells, where they are used to produce energy. Insulin, a hormone * produced by the pancreas * , helps glucose enter cells. When the body takes in more glucose than needed, the extra glucose is stored in the liver and muscles in a form called glycogen, or the extra glucose is converted into fat for storage in fat cells. The body can use the stored glucose whenever it needs energy between meals. When the level of glucose in the blood begins to fall, glucagon, another hormone produced by the pancreas, signals the liver to break down glycogen and release glucose. This response increases the blood glucose levels to the normal level. When the level of glucose in the blood begins to rise, special cells, called beta cells, signal the pancreas to release insulin so that glucose can enter cells while also reducing glucose production by the liver. This response lowers the amount of glucose in the bloodstream. As the blood glucose level returns to normal, so does the secretion of insulin from the pancreas.

Insulin-induced hypoglycemia

High Blood Sugar and Low Blood Sugar Symptoms

High Blood Sugar and Low Blood Sugar Symptoms
Table by Electronic Illustrators Group. © 2016 Cengage Learning®.
Nondiabetic hypoglycemias

In people who do not have diabetes, the three major forms of hyperglycemia are tumor-induced hypoglycemia, reactive hypoglycemia, and fasting hypoglycemia.


Hypoglycemia can occasionally be caused by an insulinoma, a tumor * of the insulin-producing cells of the pancreas. Insulinomas secrete insulin and raise insulin levels too high in relation to the blood glucose level. These tumors are very rare and do not normally spread elsewhere in the body. Other non-islet-cell tumors occurring in the chest or abdomen also secrete insulin-like growth factors that may cause hypoglycemia.


Reactive hypoglycemia occurs after eating, especially after a meal containing lots of sugary or starchy foods. The sugar from the meal causes the body to rapidly produce a great deal of insulin to prevent blood sugar from rising too high. But the body makes so much insulin that the blood sugar level drops too low instead.


Fasting hypoglycemia occurs several hours after a person's last meal. It can happen as a result of conditions such as anorexia nervosa * or starvation.

Other possible causes of low blood sugar in people without diabetes are:

* (such as Addison's disease) and the pituitary gland (such as hypopituitarism) can result in hypoglycemia because they cause a deficiency of the key hormones regulating glucose production.

How Is Hypoglycemia Diagnosed?

To find out if a person has hypoglycemia, doctors ask about symptoms and whether they go away when the person eats sugar. The doctor will also examine the patient and take a medical history to look for the specific features of disorders known to be associated with hypoglycemia. Blood tests performed when the person is having symptoms of hypoglycemia can confirm low levels of sugar in the blood, if present, and can measure the levels of insulin and other hormones and substances involved in the control of blood sugar levels. The tests can distinguish between the hypoglycemia symptoms due to adrenalin-related hormones and those due to a shortage of glucose being delivered to the brain (neuroglycopenia).

See also Anorexia Nervosa • Diabetes • Metabolic Disease


Books and Articles

“New Brain Pathway Offers Hope for Treating Hypoglycemia.” Health System, University of Michigan, January 22, 2015. http://www.uofmhealth.org/news/archive/201501/new-brain-pathway-offershope-treating-hypoglycemia (accessed July 20, 2015).

Saudek, Christopher D., Richard R. Rubin, and Thomas W. Donner. The Johns Hopkins Guide to Diabetes: For Patients and Families. 2nd ed. Baltimore: Johns Hopkins University Press, 2014.


Diabetes Care and Education. “Managing and Preventing Hypoglycemia.” Academy of Nutrition and Dietetics. http://www.ocde.us/Health/Documents/CSUF%20Skills%20Lab/6161%20Hypoglycemia%20p2.pdf (accessed June 14, 2016).


American Diabetes Association. 1701 N. Beauregard St., Alexandria, VA 22311. Toll-free: 800-342-2383. Website: http://www.diabetes.org (accessed July 20, 2015).

Centers for Disease Control and Prevention, Diabetes Home. 1600 Clifton Rd., Atlanta, GA 30329-4027. Toll-free: 800-232-4636. Website: http://www.cdc.govdiabetes/home/index.html (accessed June 24, 2016).

Hypoglycemia Support Foundation. PO Box 451778, Sunrise, FL 33345. Website: http://hypoglycemia.org (accessed July 20, 2015).

National Institute of Diabetes and Digestive and Kidney Diseases. Building 31, Room 9A04, 31 Center Dr., MSC 2560, Bethesda, MD 20892-2560. Telephone: 301-496-2560. Website: http://www.niddk.nih.gov (accessed July 20, 2015).

* diabetes (dye-uh-BEE-teez) is a condition in which the body's pancreas does not produce enough insulin or the body cannot use the insulin it makes effectively, resulting in increased levels of sugar in the blood. This can lead to increased urination, dehydration, weight loss, weakness, and a number of other symptoms and complications related to chemical imbalances within the body.

* coma (KO-ma) is an unconscious state, like a very deep sleep. A person in a coma cannot be awakened, and cannot move, see, speak, or hear.

* hormone is a chemical substance that is produced by a gland and sent into the blood-stream carrying messages that have certain effects on other parts of the body.

* pancreas (PAN-kree-us) is a gland located behind the stomach that produces enzymes and hormones necessary for digestion and metabolism.

* tumor (TOO-mor) is an abnormal growth of body tissue that has no known cause or physiologic purpose. A tumor may or may not be cancerous.

* anorexia nervosa (an-o-REK-seuh ner-VO-suh) is an emotional disorder characterized by dread of gaining weight, leading to selfstarvation and dangerous loss of weight and malnutrition.

* adrenal glands (uh-DREEN-al glands) are the pair of endocrine organs located near the kidneys.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)