How High Does a Person's Sugar Levels Have to Be to Go Into a Diabetic Coma?

A sugar level of 600 milligrams per deciliter or more can put someone into a diabetic coma, according to WebMD. A diabetic coma is also referred to as diabetic hyperosmolar syndrome. Symptoms of a diabetic coma can include an altered mental state, problems with vision, trouble speaking and paralysis..

A diabetic coma is the result of extremely high blood sugar levels. When the sugar levels are high, the blood becomes thicker and passes into the urine. This indicates that the body needs to filter out the excess sugar; otherwise, rapid dehydration, coma and even death can set in if left untreated.