What is dangerously high blood sugar?

A blood sugar level over 600 milligrams per deciliter can result in a life-threatening coma and dehydration. This condition is known as diabetic hyperosmolar syndrome. A person with this condition has blood that becomes thick like syrup, reports Mayo Clinic.

Symptoms of diabetic hyperosmolar syndrome include thirst, fever, dry mouth, confusion and loss of vision, according to Mayo Clinic. Patients with these symptoms and a high sugar level need immediate medical attention. Diabetic hyperosmolar syndrome is most common in older adults with Type 2 diabetes. The condition is treated with intravenous fluids to treat the dehydration and intravenous insulin to manage sugar levels.