Last Modified: 1:27pm 16/04/2021

How to recognise Hyperglycaemia


Patients with newly discovered hyperglycaemia have significantly higher in-hospital mortality than patients with a known history of diabetes or normoglycaemic patients.

Increasing evidence indicates that the development of hyperglycaemia during acute medical or surgical illness is not a physiological or benign condition, but is a marker of poor clinical outcome and mortality.

Both hyperglycaemia and hypoglycaemia are associated with higher mortality, independent of known history of diabetes.

BMJ Best Practice 2021

Hyperglycaemia doesn’t cause symptoms until glucose values are significantly elevated.

Symptoms of hyperglycaemia develop slowly over several days or weeks. The longer blood sugar levels stay high, the more serious the symptoms become. However, some people who’ve had type 2 diabetes for a long time may not show any symptoms despite elevated blood sugar levels.

Early signs and symptoms

The main 3 symptoms of high blood sugar levels are increased urination, increased thirst and increased hunger.

High blood sugar levels can also contribute to the following symptoms:

    • Regular/above-average urination
    • Weakness or feeling tired
    • Loss of weight
    • Increased thirst
    • Vision blurring

Later signs and symptoms

If hyperglycemia goes untreated, it can cause toxic acids (ketones) to build up in your blood and urine (ketoacidosis). Signs and symptoms include:

  • Fruity-smelling breath
  • Nausea and vomiting
  • Shortness of breath
  • Dry mouth
  • Weakness
  • Confusion
  • Coma
  • Abdominal pain

Is hyperglycemia serious?

Hyperglycemia can be serious if:

  • Blood glucose levels stay high for extended periods of time – this can lead to the development of long term complications like neuropathy and retinopathy.
  • Blood glucose levels rise dangerously high – this can lead to short term complications. Short term complications of very high blood sugar levels include ketoacidsosis and hyperosmolar hyperglycemic  syndrome. Ketoacidosis is a dangerous complication that mainly affects people with type 1 diabetes but can also affect some people with type 2 diabetes that are dependent on insulin. The risk of ketoacidosis becomes significant if blood glucose levels rise above 15 mmol/l (270 mg/dl).

Can drinking a lot of water lower your blood sugar levels?

Although feeling very thirsty is a symptom of a hyper, drinking a lot of water will not bring blood sugar levels down. It will only help to reduce a patients risk of dehydration.

It’s important that patients take their diabetes medication to bring blood sugar levels down. If patients have consistently high blood sugar levels seek senior advice and support.

Diabetes UK