Hyperosmolar Nonketotic Coma

(HHNC; Hyperosmolar Coma; Diabetic Nonketotic Coma; Hyperosmolar Nonketotic State)


Hyperosmolar nonketotic coma occurs in people with diabetes. It is a life-threatening event. Seek medical attention right away if you think you have any symptoms of an impending hyperosmolar nonketotic coma.

Causes    TOP

Hyperosmolar nonketotic coma is a complication of very high blood glucose levels. Blood glucose often rises to these levels because of an illness or infection.

The body will try to get rid of the extra blood glucose through the urine. The frequency and volume of urination will increase. Unfortunately, this process also washes out other substances in your blood. Some of these substances are important to your brain. Low levels of these substances can lead to seizures, coma, and eventually death.

Risk Factors    TOP

The chance of hyperosmolar nonketotic coma is higher in older adults.

Other factors that may increase your chance of hyperosmolar nonketotic coma include having diabetes and:

Symptoms    TOP

Symptoms that may occur before the hyperosmolar nonketotic coma may include:

  • Mental confusion
  • Seizures
  • Frequent urination
  • Nausea or vomiting
  • Dry mouth
  • Thirst
  • Warm, dry skin without sweating
  • High fever
  • Sleepiness
  • Vision loss
  • Hallucinations
  • Weakness or strange movements on one side of the body with or without seizures

Diagnosis    TOP

If you arrive at the hospital in a hyperosmolar nonketotic coma, your vital signs will be monitored. The levels of glucose and other substances in your blood will be tested with:

  • Blood tests—can also test kidney function
  • Urine tests
  • Urine, blood, and sputum cultures

An electrocardiogram (EKG) may also be done to check your heart's electrical activity.


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Treatment    TOP

You will likely need treatment in the emergency room and/or the intensive care unit at the hospital. Treatment will focus on restoring the correct balance of substances in your blood, including glucose. Treatment may include:

  • Fluids and minerals through an IV—to replace substances you lost and improve your urine output.
  • Insulin through an IV—to help control your blood glucose levels.

You may need additional treatment, such as antibiotics, if an infection led to the coma.

Prevention    TOP

To help prevent hyperosmolar nonketotic coma:

  • Monitor your blood glucose levels regularly. Your doctor can instruct you about how often to check your levels, and what the numbers mean.
  • Drink plenty of fluids throughout the day.
  • Talk with your doctor about how to manage your blood glucose when you are sick.


American Diabetes Association
National Institute of Diabetes and Digestive and Kidney Diseases


Canadian Diabetes Association


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Updated January 12, 2014. Accessed September 30, 2014.
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Hyperosmolar hyperglycemic nonketotic syndrome (HHNS). American Diabetes Association website. Available at:
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Updated December 6, 2014. Accessed September 30, 2014.
Last reviewed September 2015 by Kim Carmichael, MD
Last Updated: 9/30/2014

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