Hypoglycaemia unawareness in patients with diabetes

Hypoglycaemia unawareness occurs when the threshold for development of adrenergic (autonomic) symptoms is close to, or lower than, the threshold for neuroglycopenic symptoms. Thus, the characteristic adrenergic symptoms that indicate the onset of decreasing blood glucose concentration are absent and the first sign of hypoglycaemia is confusion or loss of consciousness. Hypoglycaemia unawareness is associated with an increased risk of severe hypoglycaemia and is more common in patients with type 1 diabetes, especially of more than 10 years duration. It may also occur in patients with type 2 or other types of diabetes, especially those treated with insulin or a sulfonylurea.

Hypoglycaemia unawareness may follow repeated episodes of short-duration hypoglycaemia. These episodes have been shown to impair the adrenergic responses to subsequent hypoglycaemia. Target glycated haemoglobin (HbA1c) should be individualised accordingly (target HbA1c may need to be slightly higher to minimise the risk of hypoglycaemia).

Hypoglycaemia unawareness and defective counter-regulatory hormone response (associated with hypoglycaemia unawareness) are potentially reversible. Strict avoidance of hypoglycaemia for a period of 2 days to 3 months has been associated with improvement in the recognition of severe hypoglycaemia, counter-regulatory hormone response or both. A continuous glucose monitoring system is beneficial to recognise patterns and times of hypoglycaemic risk. In some cases of hypoglycaemic unawareness, the patient may benefit from structured educational and psychobehavioural programs (eg blood glucose awareness training [BGAT]) to assist with recognition of hypoglycaemia. Seek advice from a multidisciplinary diabetes team.

A patient with hypoglycaemia unawareness should have their fitness to drive assessed and monitored by an experienced diabetes specialist. Occupational implications should also be considered, particularly if the patient is required to operate heavy machinery and equipment. For further information about driving for patients with diabetes, including drivers of commercial vehicles, see Driving and type 1 diabetes or Driving and type 2 diabetes.