Hyperglycemia is a medical term used to indicate the presence of high levels of sugar (glucose) in the blood compared to normal values. Normal blood glucose values ​​(blood glucose) are between 70 and 100 milligrams / deciliter (mg / dl ) after 8 hours of fasting.

Diabetes is diagnosed when fasting blood glucose levels exceed 126 mg / dL at least twice. In people with fasting blood glucose between 101 and 125 mg / dl we speak of "prediabetes". Hyperglycemia can occasionally also be present in non-diabetic people who have had a stroke or heart attack.

In people with diabetes, hyperglycemia must be carefully treated with the aim of keeping blood glucose levels as close to normal as possible. It is important to be able to recognize hyperglycemia, as if left untreated, it can cause severe health problems.

Mild episodes of hyperglycemia are usually not a cause for concern and can be treated fairly easily or can return to normal on their own.

However, hyperglycemia can become dangerous if the blood sugar is very high or stays high for long periods.

In these cases, life-threatening complications may appear, such as:

  • diabetic ketoacidosis, a serious condition in which the cells, unable to use glucose, use the fat stores and muscle as an alternative source of energy. This leads to a buildup of acidic ketone bodies in the blood, which can cause vomiting, dehydration, unconsciousness and even death.
  • hyperosmolar coma, a condition of severe dehydration due to very high levels of hyperglycemia

The constant presence of high blood sugar levels causes major complications affecting the heart, blood vessels, kidneys, eye and nerves.

If you experience episodes of hyperglycemia regularly, it is important to talk to your doctor or diabetes team as lifestyle changes or medication changes may be required to keep your blood sugar close to normal.



The symptoms of hyperglycemia are:

  • need to drink frequently(polydipsia)
  • dry mouth and throat
  • blurred vision
  • feeling tired
  • need to urinate more frequently than usual, particularly at night(polyuria)
  • unexplained weight loss
  • repeated infections, such as bladder infections (cystitis) and skin infections
  • headache

Since the symptoms of hyperglycemia may be due to diabetes, if they appear, you should contact your family doctor as soon as possible.



The main cause of hyperglycemia is undoubtedly diabetes, so much so that it is considered the criterion for diagnosing the disease.

Hyperglycemia in diabetes is caused by insulin produced in insufficient quantities by the pancreas or not functioning properly. Insulin is the hormone that regulates the entry of glucose into the body's cells and, in this way, lowers its levels in the blood.

In people with diabetes who are on adequate therapy, blood sugar can rise in some conditions which include:

  • stress
  • a disease, even a simple cold
  • excessive food intake (or not following the recommended power plan)
  • poor exercise
  • dehydration
  • missed a dose of your diabetes medicine, or taking the wrong dose
  • taking too much medication to raise blood sugar (in case of a hypoglycemic episode)
  • taking steroid drugs

Occasional episodes of hyperglycemia can also occur in children and young adults during peak growth.

There are other diseases and conditions, although rarer, that can cause hyperglycemia:

  • acromegaly, clinical syndrome due to high circulating levels of growth hormone
  • acute stress (in response to severe trauma, such as following a heart attack or stroke)
  • long-term kidney disease
  • Cushing's syndrome
  • drugs, including: corticosteroids, tricyclic antidepressants, diuretics, adrenaline, estrogen (birth control pill and hormone replacement therapy, lithium, phenytoin, aspirin
  • excessive food intake
  • hyperthyroidism
  • pancreatic cancer
  • pancreatitis
  • infections or inflammation


The diagnosis of hyperglycemia is very simple, just carry out a blood test to check the levels of glucose present in the blood (glucose test). Blood glucose values ​​are normally below 100 mg / dl after 8 hours of fasting.

The glucose dosage is normally prescribed by the doctor when a person exhibits a series of symptoms that lead him to suspect hyperglycemia, in individuals with a history of diabetes in the family or, in any case, considered at risk of developing it.

In people with diabetes, blood glucose control must be constant and can also be checked at home via a portable medical device called glucometer.

The glucose dosage can be combined with the search for glucose and ketone bodies in the urine and the dosage of glycated hemoglobin in the blood (useful for monitoring the average blood sugar levels in the last two or three months).



People with diabetes to maintain good blood sugar control and, above all, in the case of hyperglycemia, must follow the advice of the diabetes team where they are treated. Recommendations from the diabetes team include:

  • diet modification, for example, avoiding foods that raise your blood sugar, such as sugary foods or drinks
  • intake of plenty of fluids that do not contain sugar, this can help restore the right level of hydration if dehydrated
  • practicing regular exercise, engaging in moderate intensity physical activity such as brisk walking which can reduce blood sugar levels and facilitate weight loss
  • modification of insulin dosage under the supervision of the diabetes team

You may also be advised to check your blood sugar more frequently or to measure the presence of ketones (associated with diabetic ketoacidosis) in your blood or urine.

Until your blood sugar is under control again, it is advisable to watch out for the manifestation of additional symptoms that could signal a more serious illness.

When to see your doctor

It is advisable to seek immediate medical attention if high blood sugar levels are found and / or the following symptoms occur:

  • feeling tired
  • stomach ache
  • respiratory difficulties
  • signs of dehydration, such as headache, dry skin, and a weak, rapid heartbeat
  • difficulty staying awake

These symptoms could be a sign of severe hyperglycemia up to diabetic ketoacidosis or hyperosmolar hyperglycemia (see introduction) which require immediate hospitalization for treatment.

How to prevent hyperglycemia

There are simple ways to reduce the risk of severe or prolonged hyperglycemia, such as:

  • pay attentionto the power supply: be aware that snacks, sugary foods or carbohydrates can affect blood sugar (read the Hoax)
  • stick to the treatment plan: It is important to take diabetes medications as directed by the diabetes team
  • be as active as possibleRegular exercise can help control blood sugar but it is important to consult with your GP, or diabetes team, if you are taking diabetes medications as your medication may need to be adjusted to keep your blood sugar constant
  • consult the diabetes team in the event of any other disease occurring: the diabetes team can provide some information to help keep blood sugar under control during an illness
  • monitor blood sugar: the diabetes team can recommend the use of a blood glucose meter to check blood glucose levels at home and be able to intervene quickly in the event of glycemic changes


Preventing episodes of hyperglycemia and keeping blood glucose levels as close to normal as possible is possible by maintaining a correct lifestyle, in particular:

  • following a diet low in sugar and rich in plant substances (fruit and vegetables)
  • regularly engaging in moderate physical activity
  • keeping body weight under control
  • checking your blood sugar levels

People at risk of developing diabetes require constant blood glucose monitoring combined with weight control, constant physical activity, a reduction in fat intake and an increase in dietary fiber.



Untreated hyperglycemia can lead to other major health problems and cause long-term complications including:

  • cardiovascular diseases
  • damage to the nervous system (neuropathies)
  • kidney damage (diabetic nephropathy) or kidney failure
  • damage to the retina (diabetic retinopathy) which can lead to blindness
  • cataract
  • foot problems which can lead to ulceration and, in severe cases, even to amputation
  • bone problems
  • infections of various kinds

Additionally, very high blood sugar levels for prolonged periods can cause serious complications such as diabetic ketoacidosis. This is a serious condition in which the cells, not being able to use glucose, use the fat deposits and muscle as an alternative source of energy causing an accumulation of acid ketone bodies in the blood which can cause vomiting, dehydration, loss of conscience and even death.

Living with

Living with

To avoid episodes of hyperglycemia and maintain a good quality of life, it is essential to keep blood glucose levels under control and periodically carry out all the checks that the doctor will indicate.

To keep your blood sugar within normal values, it is important to follow a few simple rules:

  • eat in a healthy and balanced way
  • do not exceed the quantities of food
  • avoid sugary foods and drinks
  • engage in regular physical activity
  • keep weight under control
  • limit the consumption of alcoholic beverages
  • stop smoking
In-depth link

In-depth link

Italian Society of Diabetology

EpiCentro (ISS). Diabetes

Humanitas Research Hospital. Hyperglycemia or prediabetes

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