Hyperglycemic Hyperosmolar Nonketotic Syndrome (HHNS)

Another complication of extremely high blood glucose levels, hyperosmolar hyperglycemia syndrome (also called hyperglycemic hyperosmolar nonketotic coma or syndrome) occurs most frequently in patients with type 2 diabetes. In HHNS, hyperglycemia occurs without ketosis (the formation of ketone bodies). Extreme dehydration causes a dangerous drop in blood pressure and potential cardiovascular collapse. There is a high mortality rate with HHNS.

Often, people who develop HHNS are on drugs that raise their blood glucose levels, or become dehydrated due to diuretic medications or illness. The condition occurs commonly in elderly patients with previously undiagnosed diabetes. Having impaired kidney function also increases your risk of developing HHNS.

HHNS can occur at blood glucose levels about 600 mg/dl (33.3 mmol/l). At diagnosis, plasma glucose levels are usually much higher than in DKA (near 1000 mg/dl, or 55.5 mmol/l).


Many over-the-counter and prescription medications can raise blood glucose levels, including steroids, atypical antipsychotics, and glucocorticoids. Drugs that induce dehydration can also cause dangerous hyperglycemic episodes. Before taking any new medications, talk to your doctor about potential side effects.

Signs and Symptoms

As opposed to DKA, which usually has a rapid onset, HHNS may be subtler, taking days or weeks to build up to a crisis point. If you are ill and your glucose levels are persistently above 240 mg/dl, even if you test negative for ketones, you should still call your doctor for further advice. If you exhibit any of the signs of HHNS along with elevated blood sugar levels, call your doctor immediately or go to the nearest emergency care facility. Possible symptoms of HHNS include:

  • Frequent urination

  • Excessive thirst

  • Nausea and vomiting

  • Weight loss

  • Dehydration

  • Weakness

  • Seizures

  • Confusion, unconsciousness, or coma

Treating HHNS

Treatment for HHNS is similar to that for diabetic ketoacidosis. Restoring the fluid balance to the bloodstream is the immediate goal. A saline solution is administered via an intravenous line, and electrolytes may also be administered. Insulin therapy may or may not be needed. Finding out the root cause or event that triggered the HHNS is key to preventing its recurrence.

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