An Overview of Hyperglycemic Hyperosmolar Nonketotic Syndrome

Protecting Yourself From the Dangers of a Diabetic Coma

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Hyperglycemic hyperosmolar nonketotic syndrome (HHNS) is a potentially deadly condition that can develop as a result of infection or illness in people with uncontrolled type 2 diabetes or when diabetes medications aren't taken as directed. Some also refer to this as a "diabetic coma."


Common symptoms of HHNS include:

  • Blood glucose levels over 600 mg/dl
  • Frequent urination
  • Extreme thirst
  • Dry mouth
  • Confusion or sleepiness
  • Skin that is warm and dry without sweating
  • Fever (usually over 101 degrees Fahrenheit)
  • Weakness or paralysis on one side of the body
  • Loss of vision or hallucinations


HHNS primarily occurs in people with type 2 diabetes when glucose levels surge very high (typically above 600 mg/dl). As a result, the person becomes severely dehydrated. When blood glucose levels are extremely elevated, the blood becomes thicker and the body produces more urine as a way to lower the glucose levels.

The result is frequent urination, which can result in serious or even life-threatening dehydration. If these fluids are not adequately replenished, the condition may eventually result in a seizure, coma, or even death.

HHNS is typically brought on by: 

  • An infection, such as pneumonia or a urinary tract infection
  • Poor management of blood sugar, and/or not taking diabetes medications as prescribed
  • Taking certain medications, such as glucocorticoids (which alter glucose levels) or diuretics (which increase urine output)
  • Having chronic conditions in addition to diabetes, such as congestive heart failure or kidney disease

Most people who experience HHNS are adults age 65 and above with type 2 diabetes. But those with type 1 diabetes and the young can experience HHNS as well, although it is less common.


HHNS is diagnosed by testing blood glucose levels, which can be performed via fingerstick, and by testing serum osmolality, a test which measures the body's water/electrolyte balance.


Treatment typically involves starting intravenous fluids (saline solution) to rehydrate the body quickly. It may also require IV insulin to bring down the blood sugar levels. Potassium replenishment may also be required depending on blood potassium levels.

It is imperative that a person experiencing HHNS receive urgent professional medical care, as HHNS may be fatal.


The best way to prevent this serious condition is to manage your diabetes by:

  • Checking your blood sugar according to your doctor’s instructions. When you are sick, you should check your blood about every four hours. Your blood sugar tends to be naturally higher when your body is fighting a virus or infection.
  • Taking your diabetes medications, including insulin, as directed by your doctor
  • Drinking an ample amount of fluid each day, especially when you are ill
  • Staying in contact with your diabetes healthcare team when your blood sugar is consistently above 300 mg/dl.
  • Staying up-to-date on vaccinations, including getting your annual flu shot and speaking to your doctor about the pneumococcal vaccine, which may prevent pneumonia.

How Is HHNS Different From Diabetic Ketoacidosis (DKA)?

DKA is also a serious condition and potentially life-threatening if not treated promptly. In contrast to HHNS, DKA is almost exclusively a condition that occurs in people with type 1 diabetes.

A lack of insulin causes a build-up of glucose in the blood that cannot get into the cells of the body to be used for energy. The body compensates by looking for an alternative energy source in stored fat. When stored fat is used for energy it creates a toxic waste product called ketones, which can poison the body.

HHNS does not produce ketones, and the symptoms of DKA are different, including:

  • Breath that has a fruity odor
  • Labored breathing
  • Nausea and vomiting
  • A rapid and weak pulse
  • Abdominal pain

A Word From Verywell

The best way to prevent HHNS is by keeping your blood sugar levels under control. Test them regularly using a glucometer, work with your doctor to make sure you're taking any diabetes medications as prescribed, and learn the warning signs of elevated glucose levels and dehydration, such as extreme thirst and frequent urination, so you know to seek treatment when you need it. Educate your loved ones and coworkers to also recognize the early signs of blood sugar imbalance, so they can send for help, too.

Read more about the symptoms of hyperglycemia.

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Article Sources

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