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