Hyperglycemia, or high blood glucose, occurs when there is too much sugar in the blood. This happens when your body has too little insulin (the hormone that transports glucose into the blood), or if your body can't use insulin properly. The condition is most often linked with diabetes.
Hyperglycemia is blood glucose greater than 125 mg/dL (milligrams per deciliter) while fasting (not eating for at least eight hours; a person with a fasting blood glucose greater than 125 mg/dL has diabetes).
A person has impaired glucose tolerance, or pre-diabetes, with a fasting blood glucose of 100 mg/dL to 125 mg/dL.
A person has hyperglycemia if their blood glucose is greater than 180 mg/dL one to two hours after eating.
If you have hyperglycemia and it’s untreated for long periods of time, you can damage your nerves, blood vessels, tissues and organs. Damage to blood vessels can increase your risk of heart attack and stroke, and nerve damage may also lead to eye damage, kidney damage and non-healing wounds.