©2018 WebMD, Inc. All rights reserved. eMedicineHealth does not provide medical advice, diagnosis or treatment. See Additional Information.

Symptoms and Signs of Hypoglycemia (Low Blood Sugar)

Doctor's Notes on Hypoglycemia
(Low Blood Sugar)

Hypoglycemia is a medical problem when the concentration of glucose in the blood is below 60 mg/dL. The concentrations can affect brain function (levels below 50 mg/dL) and/or can lead to coma or even death at very low levels of glucose in the blood. Common symptoms and signs of hypoglycemia include trembling, clammy skin, heart palpitations, anxiety, sweating, hunger and/or irritability. These symptoms can be quickly relieved in most individuals when blood glucose levels are higher than 60 mg/dL; this is accomplished by the patient eating or drinking a high concentrated glucose containing substance (like sugared lemonade or a piece of hard candy) or by IV glucose-containing fluid. This rapid alteration symptoms to administration of glucose is also a sign of hypoglycemia. However, when the glucose level approaches severely low levels where the brain is derived of glucose, signs and symptoms become progressively worse; for example, severe headaches, confusion and/or loss of the ability to think, seizures, coma and even death.

There are many common causes of hypoglycemia. Most individuals that develop symptoms of hypoglycemia have diabetes that results in loss or inadequate production of insulin. Other common causes include the following; overmedication with insulin, missed meals, alcohol use, use of medications such as beta blockers and other drugs, severe infections, cancers causing poor fluid and/or food intake, adrenal insufficiency, kidney failure, liver failure, genetic defects, insulin-producing tumors and other problems.

Very low glucose levels are considered by most physicians to be a medical emergency.

Medical Author:
Medically Reviewed on 3/11/2019

(Low Blood Sugar) Symptoms

Epinephrine is among the major hormones released during hypoglycemia. Epinephrine causes the majority of the early symptoms of hypoglycemia.

Common symptoms of hypoglycemia include the following:

When the brain remains deprived of glucose, a later set of symptoms follows:

Ultimately, after significant coma or loss of consciousness, death can occur.

It is important to realize that with chronic or repeated hypoglycemia, the body does not respond as vigorously, so any hypoglycemic individual may display mild symptoms, or even experience no appreciable symptoms. Again, documentation of the blood glucose level is essential to confirm the diagnosis, with further testing to establish the specific cause if not known.

(Low Blood Sugar) 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.
  • Often a person who has more than one medical problem may become confused about how much of a certain medication they should take, or their medications may interact to cause hypoglycemia.
  • Hypoglycemia also may occur in people with cancer, which often causes loss of appetite. Many such people skip meals because they are not hungry or because chemotherapy causes foods to taste differently. To prevent this, people on chemotherapy should be encouraged by their doctors and loved ones to try to stay on special diets and take medications to keep them from feeling sick. If this does not work, special medications to help with appetite are available.
  • Adrenal insufficiency results from diseases that impair the adrenal glands, which are located above the kidneys. These small structures make certain hormones and substances, mainly cortisol and epinephrine, which also help elevate glucose in addition to their other functions. If these substances are not made, low blood pressure, hypoglycemia, or both can result.
  • The pituitary gland makes growth hormone, which also helps to maintain the balance of glucose. Deficiency of growth hormone causes hypoglycemia, especially in young infants and children.
  • Kidney failure causes hypoglycemia in three separate ways. The kidneys help to generate new glucose from amino acids (called gluconeogenesis). Gluconeogenesis is impaired in kidney failure. Also, insulin circulates for a longer period of time and is cleared slowly when kidney function is poor. The third important reason is that kidney failure reduces the appetite and consequently, oral intake of food.
  • The liver stores glucose in a form called glycogen. In the presence of liver failure, the abilities of the liver to generate new glucose and to release glucose are impaired.
  • Insulin-producing tumors of the pancreas (called insulinomas) cause hypoglycemia by releasing inappropriately high amounts of insulin. Certain tumors of the liver called hepatomas or other tumors such as fibrosarcomas and mesotheliomas can also cause hypoglycemia by producing insulin-like factors.

Blood Sugar Swings Tips for Managing Diabetes & Glucose Levels Slideshow

Blood Sugar Swings Tips for Managing Diabetes & Glucose Levels Slideshow

There are many different ways blood sugar (glucose levels in the blood) can be affected and cause problems with sugar control in people with diabetes. Each person reacts differently to various items that influence blood sugars. There are some compounds individuals with diabetes may want to examine to see how they influence their own blood sugar levels. For example, blood sugar levels can rise after drinking coffee, black tea, and some energy drinks due to the presence of caffeine. There are other compounds that may alter blood glucose levels and methods people with diabetes can use to see what compounds and actions influence their own blood sugar levels.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.