Hyperosmolar Hyperglycemic State (HHS)

Hyperosmolar hyperglycemic state (HHS) is a serious complication of diabetes that happens when blood sugar levels are very high for a long period of time. Symptoms of HHS can include extreme thirst, frequent urination and confusion. HHS is an emergency that requires immediate medical care.


What is hyperosmolar hyperglycemic state?

Hyperosmolar hyperglycemic state (HHS) is a life-threatening complication of diabetes — mainly Type 2 diabetes. HHS happens when your blood glucose (sugar) levels are too high for a long period, leading to severe dehydration and confusion.

HHS requires immediate medical treatment. Without treatment, it can be fatal.

What’s the difference between DKA and HHS?

Diabetes-related ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS) are both life-threatening diabetes complications related to high blood sugar (hyperglycemia), but they’re different conditions.

DKA happens when your body doesn’t have enough insulin. Your body needs insulin to turn glucose, your body’s go-to source of fuel, into energy. If there’s no insulin or not enough insulin, your body starts breaking down fat for energy instead. As your body breaks down fat, it releases ketones into your bloodstream. Ketones cause your blood to become acidic, which is life-threatening.

HHS happens when very high blood sugar leads to severe dehydration and highly concentrated blood (high osmolality), which are life-threatening. HHS also involves a lack of insulin, but the person usually still produces enough insulin to prevent the production of ketones. In addition, there’s usually an underlying condition, such as an infection, that’s also contributing to the high blood sugar.

The main difference between DKA and HHS is that DKA involves ketones and blood acidity; HHS doesn’t. The two complications have similar symptoms, including intense thirst, frequent urination and mental status changes.

Differences between DKA and HHS include:

People affected.
Most commonly affects people with Type 1 diabetes.
Most commonly affects people with Type 2 diabetes.
Time to develop.
Develops quickly — often within 24 hours.
Develops more slowly — usually within days to weeks.
Blood sugar level.
Usually above 250 mg/dL.
Higher than 600 mg/dL.
Urine or blood ketones.
Trace or none.
Blood pH level.
7.3 or lower.
Higher than 7.3.
Mortality rate.
About 1% to 8%.
About 10% to 20%.

How common is HHS?

It’s difficult for researchers to determine how common HHS is, but they think it’s relatively uncommon compared to other diabetes-related complications. Some studies show that about 1% of all hospital admissions for diabetes are due to HHS.


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Symptoms and Causes

What are the signs and symptoms of hyperosmolar hyperglycemic state?

Symptoms of HHS usually come on slowly and can take days or weeks to develop. Symptoms include:

  • Very high blood sugar level (over 600 mg/dL or 33 mmol/L).
  • Mental changes, such as confusion, delirium or experiencing hallucinations.
  • Loss of consciousness.
  • Dry mouth and extreme thirst (polydipsia).
  • Frequent urination.
  • Blurred vision or loss of vision.
  • Weakness or paralysis that may be worse on one side of your body.

If you or a loved one are experiencing these symptoms, get to the nearest emergency room.

What causes hyperosmolar hyperglycemic state?

Hyperosmolar hyperglycemic state happens when very high blood sugar leads to severe dehydration, highly concentrated blood and mental status changes.

If you manage diabetes well, your risk of developing HHS is low. But certain conditions and situations can trigger HHS to develop in people who aren’t managing diabetes well.

Common triggers of HHS include:

  • Infections: Infections are responsible for 50% to 60% of HHS cases. Pneumonia, urinary tract infections and sepsis are the three most commonly involved infections.
  • Stopping diabetes medications: If you stop taking your medications to manage diabetes, it’ll result in high blood sugar, which can lead to HHS. About 21% of HHS cases involve this situation.
  • Certain medications: Corticosteroids, thiazide diuretics and some atypical neuroleptics can affect carbohydrate metabolism, triggering the development of HHS.
  • Cardiovascular (heart and blood vessel) issues: Sudden and severe cardiovascular conditions, such as stroke, pulmonary embolism or heart attack, can trigger your body to release stress hormones, triggering the beginning of HHS.

When you have high blood sugar, your kidneys try to get rid of the excess sugar through your pee. Through this process, you also lose fluids (water) that your body needs.

If your blood sugar remains elevated for a long period of time, it leads to dehydration through frequent peeing. It also causes your blood to become more concentrated than normal. This is called hyperosmolarity. These health complications meet the criteria for HHS.

What are the risk factors for hyperosmolar hyperglycemic state?

HHS mainly affects people with Type 2 diabetes, typically adults older than 65 years. If diabetes is well managed, your risk of HHS is low.

The following factors can increase your risk of developing HHS:

  • Having poorly managed diabetes.
  • Being 65 or older.
  • Having other health issues, such as an infection, illness or a heart condition.


What are the complications of HHS?

If HHS isn’t treated in time, it can lead to the following complications:

Approximately 10% to 20% of cases result in death.

Diagnosis and Tests

How is hyperosmolar hyperglycemic state diagnosed?

You should seek medical attention right away if you have symptoms of HHS.

At the hospital, a healthcare provider will perform a physical exam and ask about your symptoms. They’ll order blood tests, such as a comprehensive metabolic panel, to check your blood sugar level and other measurements of your health.

A blood sugar level over 600 mg/dL (33 mmol/L) with low ketone levels points to a diagnosis of HHS.


Management and Treatment

How is hyperosmolar hyperglycemic state treated?

To treat HHS, a healthcare provider will give you IV (intravenous) medications. These include:

  • Fluids to hydrate you.
  • Electrolytes (such as potassium) to balance the minerals in your body.
  • Insulin to regulate your blood sugar levels.

Your healthcare team will also treat any underlying conditions or infections that may have caused the HHS. You’ll likely have to stay in the hospital at least overnight so your healthcare team can watch you closely for any complications.

What are the possible complications of HHS treatment?

The main possible complication of HHS treatment is if your blood sugar level drops too quickly. If it lowers rapidly, it can cause sudden shifts of fluid within your brain and lead to brain swelling (cerebral edema).

This is a rare complication, however. Healthcare providers know how to slowly and safely lower your blood sugar level.


How can I prevent hyperosmolar hyperglycemic state?

The best way to prevent HHS is by following a healthy lifestyle and managing your diabetes. You should:

  • Check your blood sugar regularly to make sure you’re staying within your target range.
  • Take your insulin and other diabetes medications as directed by your healthcare provider.
  • See your provider who helps you manage diabetes regularly, especially if you’re having difficulty managing it.
  • Follow a diet that’s healthy for you.
  • Get more rest and check your blood sugar more often when you’re sick.
  • Know the symptoms of HHS and get help right away if you have any of them.

Outlook / Prognosis

What is the prognosis for hyperosmolar hyperglycemic state?

The prognosis (outlook) for people with HHS largely depends on:

  • Your age.
  • Your overall health.
  • The severity of HHS.
  • How quickly you get treatment.

Up to 20% of people who have HHS die from the condition. People who develop coma and/or low blood pressure have a poorer prognosis.

Living With

When should I call my doctor about hyperosmolar hyperglycemic state (HHS)?

HHS is a serious medical condition. If you have diabetes, you should call 911 or seek emergency medical help if you:

  • Ever have a blood sugar level over 600 mg/dL.
  • Are confused or disoriented.
  • Have changes in your vision.
  • Feel weak or paralyzed anywhere in your body.

If you’ve had HHS, you’ll need to work closely with your provider once you’re home from the hospital. You can reduce your risk of developing HHS again by managing your diabetes, your diet and your lifestyle.

A note from Cleveland Clinic

Hyperosmolar hyperglycemia state (HHS) is a serious and life-threatening condition, so acting fast if you’re experiencing symptoms is very important. Call 911 or go to the nearest emergency room if you experience symptoms. Diabetes complications can be scary. Being educated and prepared are crucial to preventing HHS. Don’t be afraid to ask your healthcare provider questions about HHS or your diabetes management.

Medically Reviewed

Last reviewed on 02/17/2023.

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