Hyperosmolar Syndrome

Reviewed by: HU Medical Review Board | Last reviewed: March 2021.

Diabetes is a disease that impacts how the body uses glucose, a sugar that is the main source of energy for the body. Normally, you eat and get glucose from the food into your bloodstream, or your liver makes glucose. Your pancreas makes insulin, a hormone that helps get the glucose into the cells of your body. The cells then use glucose to fuel your body.1,2

With type 2 diabetes, your body cannot use insulin the way it should. The glucose cannot enter your cells the way it should, leaving the glucose in your bloodstream. This increases glucose (sugar) levels in your blood. Increased blood sugar leads to many problems in the body and makes you sick.1

One serious complication of high blood glucose is hyperosmolar hyperglycemic syndrome.

What is hyperosmolar hyperglycemic syndrome?

Hyperosmolar hyperglycemic syndrome (HHS) is a serious complication of diabetes. HHS most often affects those with type 2 diabetes. The death rate of HHS can be as high as 20 percent, and the condition is a medical emergency.3

Because glucose is not entering the cells the way it should, there is a state of starvation in the tissues that cannot use glucose for energy. This starvation state “tricks” the body into thinking that it needs more glucose, increasing blood sugar even further. This causes a vicious cycle of glucose that cannot enter the cells for energy and the release of more glucose from the body.3

The term “hyperosmolar” is when the blood has too much sugar and salt. This causes the body to release water, electrolytes, and sugar by urination. Too much urination and water loss leads to severe dehydration. Once dehydrated, your kidneys are no longer able to release the glucose (sugar). As a result, your blood sugar may get dangerously high, sometimes as much as 10 times the normal level.1-4


Hyperosmolar hyperglycemic syndrome is usually caused by another event or condition. The most common cause of HHS is an underlying infection that has not been treated. Other causes may include:3-5

  • Not taking your diabetic medicines, including insulin
  • Any stressful event or illness, such as stroke, heart attack, or recent surgery
  • Drugs or conditions that increase fluid or urine loss
  • Drugs or conditions that may decrease the effectiveness of insulin
  • Not drinking enough water over a period of time


Symptoms of hyperosmolar hyperglycemic syndrome can develop over several days before needing hospitalization. Early symptoms include:3-7

  • Excessive urination, known as polyuria
  • Excessive thirst, known as polydipsia
  • Weight loss
  • Dry skin and mouth
  • Rapid heart rate

As blood sugar levels continue to rise, neurologic (brain and nervous system) symptoms may occur:3-7

  • Feeling extremely tired
  • Difficulty awakening
  • Coma, in late stages

What tests diagnose hyperosmolar hyperglycemic syndrome?

Blood tests are the main way that doctors diagnose HHS. These tests determine if you are experiencing HHS or diabetic ketoacidosis (DKA), another medical emergency involving high blood sugar.8

Tests used to diagnose HHS include:8

You may require additional tests, depending on your symptoms and the severity of the condition.

How is it treated?

Treatment of HHS focuses on replacing the fluid lost inside your body and decreasing your blood sugar levels. Treatment will vary depending on the severity of the condition, but includes:8

  • Aggressive intravenous (IV, or through the veins) fluid replacement
  • Managing and replacing electrolytes
  • IV insulin
  • Treating the underlying reason that caused HHS

What can I do to prevent hyperosmolar hyperglycemic syndrome?

You may be able to decrease your chances of having DKA or HHS. Consider these steps of prevention:4,5,7

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