When your blood glucose levels are 15 mmol/L or higher, it’s called hyperglycaemia.

Symptoms of hyperglycaemia

You might experience some of the following symptoms:

  • Excessive thirst
  • Frequently passing large volumes of urine
  • Feeling tired
  • Blurred vision
  • Infections (eg thrush, cystitis, wound infections)
  • Headaches
  • Abdominal pain

Some of the causes of high glucose levels are:

  • Infection
  • Sickness
  • Stress
  • Too much carbohydrate
  • Not enough insulin

Illnesses and infections usually cause a rise in blood glucose levels. If you live with diabetes and you become unwell it’s important to follow your personalised sick day management plan. If you haven’t already developed a sick day management plan it is recommended to prepare one with your diabetes team.

Read our factsheet for more information on sick day management for people with type 1 diabetes.

When to take action

As a general rule, if you are unwell you should check your blood glucose levels at least every two hours. If your levels remain at 15 mmol/L or higher for more than 24 hours, and especially if you are unwell, you should seek advice from your doctor or diabetes team.

If you are living with Type 1 diabetes you may also need to check your ketones – either by a urine or finger-tip blood check. Your diabetes team will advise you if this is a necessary part of your diabetes management regime.

Very high blood glucose levels can lead to serious conditions (such as diabetic ketoacidosis in type 1 diabetes, or hyperosmolar hyperglycaemia in type 2) which can become life threatening.

When to seek medical attention

Signs and symptoms of hyperglycaemia which indicate you should seek urgent medical attention include:

  • High blood glucose level (especially with ketones present > 1.0 on blood check if monitoring)
  • Abdominal pain
  • Vomiting
  • Dehydration
  • Rapid, shallow breathing
  • Acetone smell on the breath
  • Confusion
  • Drowsiness (which may lead to coma)

These are medical emergencies and require treatment at a hospital.

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