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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.


It’s especially important to know the early signs of hyperglycemia if you have type 1 diabetes. If hyperglycemia is left untreated in people with type 1 diabetes, it can develop into ketoacidosis, where ketones, which are toxic acids, build up in the blood. This condition is an emergency situation that can lead to coma or death.

Early symptoms of hyperglycemia include:

High blood sugar.

Increased thirst and/or hunger.

Blurred vision.

Frequent urination (peeing).


Additional symptoms include:

Fatigue (feeling weak, tired).

Weight loss.

Vaginal and skin infections.

Slow-healing cuts and sores.

Symptoms of ketoacidosis are:



Unusual fruity smell on the breath.

Deep labored breathing or hyperventilation.

Rapid heartbeat.

Confusion and disorientation.



The dose of insulin or oral diabetes medication that you are taking is not the most helpful dose for your needs.

Your body isn’t using your natural insulin effectively (type 2 diabetes).

The amount of carbohydrates you are eating or drinking is not balanced with the amount of insulin your body is able to make or the amount of insulin you inject.

You are less active than usual.

Physical stress (from illness, a cold, the flu, an infection, etc.) is affecting you.

Emotional stress (from family conflicts, emotional problems, school or work stresses, etc.) is affecting you.

You are taking steroids for another condition.

The dawn phenomenon (a surge of hormones the body produces every morning around 4 am to 5 a.m.) is affecting you.

Other possible causes

Endocrine conditions, such as Cushing syndrome, that cause insulin resistance.

Pancreatic diseases such as pancreatitis, pancreatic cancer and cystic fibrosis.

Certain medications (such as diuretics and steroids).

Gestational diabetes, which happens in 4% of pregnancies, and is due to decreased insulin sensitivity.

Surgery or trauma.

Risk factors

Not using enough insulin or oral diabetes medication.

Not injecting insulin properly or using expired insulin.

Not following your diabetes eating plan.

Being inactive.

Having an illness or infection.

Using certain medications, such as steroids.

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Cardiovascular disease.

Nerve damage (neuropathy)

Kidney damage (diabetic nephropathy) or kidney failure.

Damage to the blood vessels of the retina (diabetic retinopathy), potentially leading to blindness.


Exercise to help lower blood sugar. Work with your healthcare provider to make a daily activity plan.

Follow your meal plan if you have one. ...

Maintain a healthy weight.

Don't smoke.

Limit drinking alcohol.