Hyperglycemia is a blood glucose concentration > 150 mg/dL (> 8.3 mmol/L). In the short term, prolonged periods of hyperglycemia may cause high urine output with dehydration.

Symptoms of hyperglycemia
The following symptoms may be associated with acute or chronic hyperglycemia:
1. Polyphagia - frequent hunger, especially pronounced hunger
2. Polydipsia - frequent thirst, especially excessive thirst
3. Polyuria - frequent urination, especially excessive urination
4.Blurred vision
5. Fatigue
6.Weight loss
7. Poor wound healing
8.Dry mouth
9. Dry or itchy skin
10. Impotence

Frequent hunger without other symptoms can also indicate that blood sugar levels are too low. This may occur when people who have diabetes take too much oral hypoglycemic medication or insulin for the amount of food they eat. The resulting drop in blood sugar level to below the normal range prompts a hunger response. This hunger is not usually as pronounced as in Type I diabetes, especially the juvenile onset form, but it makes the prescription of oral hypoglycemic medication difficult to manage.
Polydipsia and polyuria occur when blood glucose levels rise high enough to result in excretion of excess glucose via the kidneys (glycosuria), producing osmotic diuresis.
Symptoms of acute hyperglycemia may include:
1. Ketoacidosis
2. A decreased level of consciousness or confusion
3. Dehydration due to glycosuria and osmotic diuresis
4. Acute hunger and/or thirst
5. Impairment of cognitive function, along with increased sadness and anxiety