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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.


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

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 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

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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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.


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

Health Canada


Chiasson JL, Aris-Jilwan N, Belanger R, et al. Diagnosis and treatment of diabetic ketoacidosis and the hyperglycemic hyperosmolar state. Can Med Assoc J. 2003;168(7):859-866.

Hyperglycemic hyperosmolar state in adults. EBSCO DynaMed website. Available at: Updated January 12, 2014. Accessed September 30, 2014.

Kim DW, Moon Y, Gee Noh H, Choi JW, Oh J. Blood-brain barrier disruption is involved in seizure and hemianopsia in nonketotic hyperglycemia. Neurologist. 2011;17(3):164-166.

Kitabchi AE, Nyenwe EA. Hyperglycemic crises in diabetes mellitus: diabetic ketoacidosis and hyperglycemic hyperosmolar state. Endocrinol Metab Clin North Am. 2006;35(4):725-751.

Ondo WG. Hyperglycemic nonketotic states and other metabolic imbalances. Handb Clin Neurol. 2011;100:287-291.

Stoner GD. Hyperosmolar hyperglycemic state. Am Fam Physician. 2005;71(9):1723-1730.

Hyperosmolar hyperglycemic nonketotic syndrome (HHNS). American Diabetes Association website. Available at: Updated December 6, 2014. Accessed September 30, 2014.

Last reviewed September 2015 by Kim Carmichael, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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