It is important for people with diabetes to know the symptoms of high and low sugar levels so appropriate action can be taken to prevent health problems occurring in either the short or long term.

In the case of low blood glucose levels, it is generally only people on certain medications such as insulin and tablets which directly stimulate insulin production that need to be actively aware of low blood sugar symptoms.

Symptoms of high sugar levels (hyperglycemia)

One or more of the following symptoms are common when blood glucose levels are too high:

  • Increased urination
  • Increased thirst
  • Increased hunger
  • Fatigue
  • Dry mouth
  • Dry eyes
  • Blurred vision

If sugar levels are regularly too high for a number of days or weeks, the following symptoms may also be

  • Slow healing of wounds
  • Loss of weight, particularly muscle mass
  • Regular urinary tract infections (UTIs)
  • Regular episodes of thrush (yeast infections)

Note that in people that are overweight, loss of weight may sometimes be more recognisable as a loss of muscle mass.

High blood sugar can be uncomfortable and can increase the risk of developing long term complications if extended periods of hyperglycemia become a regular occurrence.

  • Read more about hyperglycemia.

Symptoms of low sugar levels (hypoglycemia)

One or more of the following symptoms may be recognised if blood glucose levels become too low:

  • Increased hunger
  • Pale appearance
  • Feeling weak
  • Lethargy
  • Faster heart rate
  • Sweating
  • Blurred vision
  • Dizzy spells
  • Reduced co-ordination
  • Impaired ability to make decisions

Hypoglycemia, or hypos for short, can be dangerous for people on the following anti-diabetic medications:

  • Insulin
  • Sulphonylureas
  • Prandial glucose regulators (glinides)

People with diabetes on these medications need to be able to spot the signs of low blood sugar levels quickly and then treat the hypo before it becomes dangerous.

Signs of very high blood glucose levels

If blood glucose levels go very high, any of the following symptoms may occur:

  • Extreme thirst
  • Dehydration
  • Nausea
  • Vomiting
  • Laboured breathing
  • Confusion
  • Coma

Very high blood glucose levels can be immediately dangerous, so if you or nayone with diabetes has symptoms of very high sugar levels, call for emergency help.

Two short term complications of diabetes that can result from very high sugar levels are:

  • Hyperosmolar Hyperglycemic State – a condition more likely to affect people with insulin resistance, such as people with type 2 diabetes
  • Diabetic Ketoacidosis – a condition more likely to affect people who are dependent on taking insulin, particularly, but not limited to, people with type 1 diabetes

Signs of very low blood glucose levels

If blood glucose levels become very low, known as severe hypoglycemia, the following symptoms may occur:

  • Slurred speech
  • Difficulty walking or standing
  • Confusion
  • Irrational, and sometimes violent, behaviour
  • Fits / convulsions
  • Loss of consciousness, which can develop into a coma
  • Death as a result of a diabetic coma