Hyperglycemia (high blood glucose levels) is the medical name for high levels of blood glucose – the characteristic of all forms of undiagnosed diabetes mellitus.

Having too much sugar in your bloodstream can pose an immediate health risk, while regular periods of high blood glucose can lead to the development of health problems referred to as long term diabetes complications.

What counts as hyperglycemia?

Hyperglycemia is defined by the American Diabetes Association as having a blood glucose level that is:

  • Higher than 130 mg/dL (milligrams/deciliter) when fasting
  • Equal or greater than 180 mg/dL (milligrams/deciliter) two hours after eating a meal

‘Normal’ blood glucose targets vary slightly depending on your type of diabetes and whether you’re a child or adult, and in some cases people may have different targets set for them by their health team.

What are the signs of hyperglycemia?

The main symptoms of high blood sugar levels are:

Other common symptoms that can occur following prolonged periods of high blood glucose include:

Very high blood sugar levels can lead to more severe symptoms such as:

  • Dehydration
  • Nausea
  • Vomiting
  • Loss of consciousness
  • Coma

These more severe symptoms may indicate the presence of dangerous conditions such as diabetic ketoacidosis (DKA), which affects people that are insulin dependent, and Hyperosmolar Hyperglycemic State (HHS), which can affect people with type 2 diabetes.

If you or someone else with diabetes is experiencing these symptoms, call the emergency services for help.

Causes of high blood sugar

The underlying causes of hyperglycemia in people with diabetes are usually from the loss of insulin producing cells in the pancreas or insulin becoming less effective on the body.

Other common factors that can lead to high blood sugar levels include:

  • eating too much carbohydrate for your medication to cope with
  • missing or delaying medication
  • being ill or stressed

Some people may also find that skipping a meal causes a rise in blood glucose levels. This can occur if your body releases glycogen, a stored form of sugar, from the liver to try to compensate for not having a meal.

Treatment for hyperglycemia

Treatment for hyperglycemia can depend on how high your glucose levels are and how your diabetes is treated.

People on insulin may wish to treat high sugar levels by taking additional insulin. Note that taking additional insulin can raise the risk of low blood glucose levels (hypoglycemia) and so this treatment is only recommended in people that have been approved by their health team to adjust their own insulin doses.

If you have type 1 diabetes and sugar levels above 240 mg/dL, it’s recommended to perform a test for ketone levels.

For people not on insulin, high blood glucose levels will often get resolved by your body, but if the high sugar levels persist you should seek advice from your doctor on how to get your them back to normal.

Preventing high sugar levels

While reducing high blood glucose is the focal point of diabetes treatment, preventing blood glucose levels from rising too high is one of the prime goals of diabetes management.

You can help keep your blood sugar levels stable by:

  • regularly taking physical activity
  • ensuring your diet is well balanced and not overly reliant on processed foods
  • getting a good balance between your intake of carbohydrates and any medication you take

Read more about management your diabetes.