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Hyperglycaemia is the medical term for a high blood sugar (glucose) level. It's a common problem for people with diabetes.
Hyperglycaemia shouldn't be confused with hypoglycaemia, which is when a person's blood sugar level drops too low.
This information focuses on hyperglycaemia in people with diabetes.
The aim of diabetes treatment is to keep blood sugar levels as near to normal as possible. But if you have diabetes, no matter how careful you are, you're likely to experience hyperglycaemia at some point.
It's important to be able to recognise and treat hyperglycaemia, as it can lead to serious health problems if left untreated.
Occasional mild episodes aren't usually a cause for concern and can be treated quite easily or may return to normal on their own. However, hyperglycaemia can be potentially dangerous if blood sugar levels become very high or stay high for long periods.
Very high blood sugar levels can cause life-threatening complications, such as:
Regularly having high blood sugar levels for long periods of time (over months or years) can result in permanent damage to parts of the body such as the eyes, nerves, kidneys and blood vessels.
If you experience hyperglycaemia regularly, speak to your doctor or diabetes care team. You may need to change your treatment or lifestyle to keep your blood sugar levels within a healthy range.
Symptoms of hyperglycaemia in people with diabetes tend to develop slowly over a few days or weeks. In some cases, there may be no symptoms until the blood sugar level is very high.
Symptoms of hyperglycaemia include:
Symptoms of hyperglycaemia can also be due to undiagnosed diabetes, so see your GP if this applies to you. You can have a test to check for the condition.
When you're first diagnosed with diabetes, your diabetes care team will usually tell you what your blood sugar level is and what you should aim to get it down to.
You may be advised to use a testing device to monitor your blood sugar level regularly at home. Alternatively, you may have an appointment with a nurse or doctor every few months to see what your average blood sugar level is – this is known as your HbA1c level.
Target blood sugar levels differ for everyone, but generally speaking:
The Diabetes UK website has more about blood sugar levels and testing.
A variety of things can trigger an increase in blood sugar level in people with diabetes, including:
Occasional episodes of hyperglycaemia can also occur in children and young adults during growth spurts.
If you've been diagnosed with diabetes and you have symptoms of hyperglycaemia, follow the advice your care team has given you to reduce your blood sugar level.
If you're not sure what to do, contact your GP or care team.
You may be advised to:
You may also be advised to monitor your blood sugar level more closely, or test your blood or urine for substances called ketones (associated with diabetic ketoacidosis).
Until your blood sugar level is back under control, watch out for additional symptoms that could be a sign of a more serious condition (see below).
Contact your diabetes care team immediately if you have a high blood sugar level and experience the following symptoms:
These symptoms could be a sign of diabetic ketoacidosis or a hyperosmolar hyperglycaemic state (see above) and you may need to be looked after in hospital.
There are simple ways to reduce your risk of severe or prolonged hyperglycaemia: