Hyperosmolar Hyperglycemic Nonketotic Syndrome

Hyperosmolar Hyperglycemic Nonketotic Syndrome

Also called: NKHH, Hyperosmolar Hyperglycemic Nonketotic State, HHNS, Hyperglycemic Hyperosmolar State, Nonketosis Hyperosmolar Hyperglycemia, HHS


Hyperosmolar hyperglycemic nonketotic syndrome (HHNS) is a dangerous condition in which a person experiences very high glucose (blood sugar) and dehydration.

One-third of all cases of HHNS occur in people with undiagnosed diabetes, according to the American Diabetes Association. It is most often found in older people with type 2 diabetes.

The condition can be triggered by causes such as an illness, infection or medication error. Left untreated, HHNS can lead to seizures, diabetic coma or death.

People with diabetes should be aware of the signs and symptoms of HHNS. The condition typically has a slow onset, over several days to weeks, and its initial symptoms are mild. Patients who experience symptoms should contact their physician. HHNS is an emergency requiring immediate medical attention.

About HHNS

Hyperosmolar hyperglycemic nonketotic syndrome (HHNS) is a serious condition involving very high blood glucose (above 600 milligrams per deciliter, mg/dL) and dehydration. HHNS is most common in older people with type 2 diabetes, but it can also occur in younger people and in patients with type 1 diabetes or other forms of diabetes. One-third of all cases of HHNS are caused by undiagnosed diabetes, according to the American Diabetes Association.

When glucose in the bloodstream rises to unhealthy levels (hyperglycemia), the body tries to dispose of the excess glucose by passing it into the urine. The kidneys excrete additional water to dilute the glucose. As a result, people begin to urinate more frequently. As time goes on, urination becomes less frequent and the urine becomes dark.

As a result of the increased urination (polyuria), the body loses a lot of water. When water is limited in the body, the kidneys conserve fluid, causing glucose levels to rise even higher. If a person does not drink enough liquids at this point, even if not thirsty, dehydration may develop.

A patient may delay seeking medical treatment because the initial symptoms of HHNS are often mild. However, once dehydration develops, brain function becomes impaired as the blood becomes thicker and more concentrated with glucose, sodium and other substances (hyperosmolarity). The patient may become confused or lethargic. Left untreated, HHNS can lead to seizures, diabetic coma and possibly death.

People with diabetes should consult in advance with their physician about their target glucose level, frequency of glucose monitoring and what action to take for the various levels of high glucose. HHNS is a hyperglycemic emergency requiring the patient to be taken to a hospital immediately.

HHNS is also known by many other names. These include hyperosmolar hyperglycemic state and nonketotic hyperosmolar state.

Severe hyperglycemia can also result in a separate condition known as diabetic ketoacidosis, which is most common in people with type 1 diabetes. Although some symptoms of HHNS are similar to those of ketoacidosis, HHNS produces few if any ketones (an acidic waste product) in the blood or urine. The mortality rate from both conditions has plunged in recent decades, according to the U.S. Centers for Disease Control and Prevention.

Risk factors and causes of HHNS

Hyperosmolar hyperglycemic nonketotic syndrome (HHNS) occurs most often in people with type 2 diabetes and is most commonly diagnosed in people over age 60. This increased risk may be due to an impaired thirst mechanism and restricted mobility in the elderly, among other factors. The condition is also more common in people with undiagnosed diabetes or unstable diabetes.

HHNS is caused by dehydration and an increase in the concentration of glucose (blood sugar), sodium and other substances in the blood (hyperosmolarity). It is usually triggered by something else, such as an illness or infection. Common triggers of HHNS include:

  • Kidney disorders
  • Heart failure
  • Recent discontinuation, insufficient amount or missed dose of insulin or antidiabetic agents
  • Certain medications (e.g., corticosteroids, diuretics, beta blockers)
  • Stress
  • Drug abuse or excessive consumption of alcohol
  • Overeating (polyphagia)
  • Inactivity
  • Chronic illness
  • Recent surgery

Signs and symptoms of HHNS

Hyperosmolar hyperglycemic nonketotic syndrome (HHNS) is a serious condition that can lead to seizures, diabetic coma and eventually death. People with diabetes should be aware of its signs and symptoms so they can immediately seek treatment when these indicators appear. Signs and symptoms include:

  • Glucose (blood sugar) level over 600 milligrams per deciliter (mg/dL)
  • Dry, parched mouth
  • Polydipsia (excessive thirst)
  • Polyuria (increased urination)
  • Warm, dry skin that does not sweat
  • High fever (above 100.4 degrees Fahrenheit, 38 degrees Celsius)
  • Low systolic blood pressure (less than 100 millimeters of mercury [mm/Hg])
  • Sleepiness
  • Confusion
  • Vision loss
  • Hallucinations
  • Weakness on one side of the body
  • Impaired speech

Diagnosis and treatment of HHNS

People who experience any of the symptoms of hyperosmolar hyperglycemic nonketotic syndrome (HHNS) should contact their physician. Their glucose (blood sugar) should be checked with a glucose test. If their blood glucose level is at or above 500 milligrams per deciliter (mg/dL), it is an emergency situation and they should be taken to a hospital immediately.

To diagnose HHNS, a physician will evaluate a patient’s medical history and perform a physical examination.

The physician will check the patient’s vital signs, which include temperature, heart rate and blood pressure. A patient with HHNS may have a temperature above 100.4 degrees Fahrenheit (38 degrees Celsius), a heart rate greater than 100 and a low systolic blood pressure.

A blood test will be performed to analyze concentrations of glucose, particles and sodium. HHNS may be diagnosed when the patient has severely elevated blood glucose levels (above 600 mg/dL), as well as elevated serum osmolality (concentration of particles) and elevated serum sodium. Osmolality increases with dehydration, and the sodium levels of the blood reflect the balance between the body’s intake and output of fluid. A high concentration of sodium in the blood (hypernatremia) usually results from excessive loss of water.

The physician may also perform additional tests to pinpoint the cause of the HHNS. Possible tests include a chest x-ray, blood cultures, urinalysis and an electrocardiogram (EKG).

The treatment of HHNS centers on correcting the patient’s dehydration, hyperglycemia and electrolyte imbalances.

The patient may receive intravenous fluid to correct the dehydration and restore electrolytes. Small doses of intravenous insulin may be given to treat the hyperglycemia. When HHNS is determined to be caused by an infection or other illness, that condition may receive treatment as well.

Once emergency treatment is started, the condition can be resolved within hours. However, some symptoms (e.g., confusion, impaired speech, hallucinations) may take three to five days to resolve completely.

Prevention methods for HHNS

The best strategy for preventing hyperosmolar hyperglycemic nonketotic syndrome (HHNS) is to prevent the underlying conditions that trigger it. Methods for people with diabetes to avoid hyperglycemia and dehydration include:

  • Following the physician-recommended diabetes management plan. Patients should follow their exercise schedule, diet and schedule of insulin or antidiabetic agents to avoid high glucose (blood sugar).
  • Checking glucose regularly. Regular glucose monitoring can alert patients to hyperglycemia. Patients can then follow steps recommended by their physician to lower glucose and prevent HHNS from developing. A physician can recommend how often testing is necessary.
  • Knowing the symptoms of hyperglycemia. Patients should be familiar with the symptoms of high glucose so they can treat it early and prevent HHNS.
  • Being informed about HHNS. People with diabetes should know the signs, symptoms and causes of HHNS, and know what actions need to be taken and at what times. Patients should know when to contact their physician, when to go to the emergency room, and how to prevent, recognize and treat dehydration and infection.
  • Having a sick-day management plan. Patients and their physician should prepare a plan for sick days in advance. Because illness can put physical stress on the body and raise glucose levels, a patient may have to take special steps to control glucose levels and avoid dehydration. Physicians can recommend when they should be contacted, how often to test glucose and ketone levels, what glucose goals should be, what medicines to take, how to suppress fever and infection, and what to eat and drink. Because illness often triggers HHNS, patients should also be aware of the condition’s symptoms and call their physician when they appear.
  • Getting vaccinated. Because HHNS is usually triggered by illness or infection, people with diabetes can protect themselves from some conditions by getting a pneumonia shot once and a flu shot annually. Patients who are 65 and those suffering from chronic illness or a weakened immune system may require an additional pneumonia shot five to 10 years after their first one.
  • Talking to a physician or pharmacist about nondiabetes medication. Certain medications (such as diuretics, beta blockers corticosteroids, estrogens, HIV drugs, antidepressants, antipsychotics, anticonvulsants and chemotherapy drugs) can raise blood glucose and/or increase urination. Patients may need to test their glucose more often when taking these medications.
  • Wearing a medical alert bracelet or carrying a medical identification card. People with diabetes are advised to wear a medical identification bracelet or necklace at all times. Patients can also carry a medical identification card in their wallet to alert family, friends, teachers, coworkers and emergency personnel. Because HHNS can cause confusion, hallucinations and impaired speech, the people around the patient may need to seek emergency treatment for the person with diabetes.
  • Managing stress. Mental stress releases hormones that raise glucose levels. Under stress, people with diabetes may test their glucose less often and stray from their diabetes management plan. Patients should discuss stress management techniques with their physician and test their glucose levels more often in stressful times.
  • Avoiding excessive amounts of alcohol. Drinking large amounts of alcohol can lead to increased urination (polyuria) and dehydration. Patients should discuss alcohol intake with their physician because some people with diabetes may need to abstain from it.

Questions for your doctor regarding HHNS

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about hyperosmolar hyperglycemic nonketotic syndrome (HHNS):

  1. Can anyone with diabetes develop HHNS? Am I at high risk?
  2. What signs and symptoms should I watch for?
  3. What actions should I take if I suspect I may be developing HHNS? How often should I test my blood sugar?
  4. How much water should I drink to avoid dehydration?
  5. When is it necessary for me to seek medical attention? At what point do signs of HHNS indicate I should be taken to a hospital?
  6. How would I be treated for HHNS?
  7. Do I need to reduce or halt use of any medications when experiencing HHNS?
  8. How long will it take me to recover from a bout of HHNS?
  9. Will you devise a sick-day plan to reduce my risk of HHNS and other diabetic complications?
  10. Is there anything else I can do to prevent HHNS?
  11. What do I need to know if a loved one is at risk of HHNS?
Scroll to Top