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.