Hyperglycemia usually doesn't cause symptoms until blood sugar (glucose) levels are high — above 180 to 200 milligrams per deciliter (mg/dL), or 10 to 11.1 millimoles per liter (mmol/L). Symptoms of hyperglycemia develop slowly over several days or weeks. The longer blood sugar levels stay high, the more serious symptoms may become. But some people who've had type 2 diabetes for a long time may not show any symptoms despite high blood sugar levels. Early signs and symptoms Recognizing early symptoms of hyperglycemia can help identify and treat it right away. Watch for: 
Frequent urination
Increased thirst
Blurred vision
Feeling weak or unusually tired
  Later signs and symptoms If hyperglycemia isn't treated, it can cause toxic acids, called ketones, to build up in the blood and urine. This condition is called ketoacidosis. Symptoms include: 
Fruity-smelling breath
Dry mouth
Abdominal pain
Nausea and vomiting
Shortness of breath
Confusion
Loss of consciousness
