Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Hyperosmolar Hyperglycemic State (HHS)

(Nonketotic Hyperosmolar Syndrome; Nonketotic Hyperosmolar Coma)


Erika F. Brutsaert

, MD, New York Medical College

Last full review/revision Sep 2020| Content last modified Sep 2020
Click here for the Professional Version

Hyperosmolar hyperglycemic state is a complication of diabetes mellitus that most often occurs in type 2 diabetes.

  • Symptoms of hyperosmolar hyperglycemic state include extreme dehydration and confusion.

  • Hyperosmolar hyperglycemic state is diagnosed by blood tests that show very high levels of glucose and very concentrated blood.

  • Treatment is intravenous fluids and insulin.

  • Complications include coma, seizures, and death.

(See also Diabetes Mellitus.)

There are two types of diabetes mellitus, type 1 and type 2. In type 1 diabetes, the body produces almost no insulin, a hormone produced by the pancreas that helps sugar (glucose) move from the blood into the cells. In type 2 diabetes, the body produces insulin, but cells fail to respond normally to the insulin. In both types of diabetes, the amount of sugar (glucose) in the blood is elevated.

If people with type 1 diabetes receive no insulin, or they need more insulin because of an illness, fat cells begin breaking down to provide energy. Fat cells that break down produce substances called ketones. Ketones provide some energy to cells but also make the blood too acidic (ketoacidosis). Diabetic ketoacidosis is a dangerous, sometimes life-threatening, disorder.

Because people with type 2 diabetes produce some insulin, ketoacidosis does not usually develop even when type 2 diabetes is untreated for a long time. However, with hyperosmolar hyperglycemic state, the blood glucose levels can become extremely high (even exceeding 1,000 milligrams per deciliter [mg/dL], or 55.5 millimoles per liter [mmol/L] of blood). Such very high blood glucose levels cause the person to pass large amounts of urine, which eventually causes severe dehydration and makes the person's blood abnormally concentrated (hyperosmolar). Thus, the disorder is called hyperosmolar hyperglycemic state.

Causes of HHS

Hyperosmolar hyperglycemic state can occur for two main reasons

  • People stop taking the drugs for their diabetes

  • An infection or other illness stresses the body

Also, certain drugs, such as corticosteroids, can raise blood glucose levels and cause hyperosmolar hyperglycemic state. Drugs such as diuretics, which people often take to treat high blood pressure, can worsen dehydration and trigger hyperosmolar hyperglycemic state.

Symptoms of HHS

The main symptom of hyperosmolar hyperglycemic state is a mental change. The change ranges from mild confusion and disorientation to drowsiness and coma. Some people have seizures and/or temporary partial paralysis resembling a stroke. Up to 20% of people die. Other symptoms that may precede the change in mental state include frequent urination and extreme thirst.

Diagnosis of HHS

  • Blood tests to measure glucose level

Doctors suspect the diagnosis of hyperosmolar hyperglycemic state when people who have recently developed confusion are found to have a very high blood glucose level. They confirm the diagnosis by doing additional blood tests that show very concentrated blood and low ketones or acidity in the bloodstream.

Treatment of HHS

  • Fluids and electrolytes given by vein

  • Insulin given by vein

Hyperosmolar hyperglycemic state is treated much like diabetic ketoacidosis. Fluids and electrolytes must be replaced intravenously. Usually, people are given insulin intravenously so that it works quickly and the dose can be adjusted frequently. The level of glucose in the blood must be restored to normal gradually to avoid sudden shifts of fluid within the brain. The blood glucose level tends to be more easily controlled than in diabetic ketoacidosis, and blood acidity problems are not severe.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Test your knowledge

Drug Treatment of Diabetes Mellitus
Many people with diabetes mellitus require drugs to lower blood glucose levels, relieve symptoms, and prevent complications. Insulin is a commonly-needed drug by people with both type 1 and type 2 diabetes. Which of the following is NOT one of the forms in which insulin is currently available?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID