Table of Contents

3.2.1 Hypoglycaemia

Definition: severe hypoglycaemic event

For the purposes of this document, a ‘severe hypoglycaemic event’ is defined as an event of hypoglycaemia of sufficient severity such that the person is unable to treat the hypoglycaemia themselves and thus requires an outside party to administer treatment. It includes hypoglycaemia causing loss of consciousness or seizure. It can occur during driving or at any other time of the day or night. A severe hypoglycaemic event is particularly relevant to driving because it affects brain function and may cause impairment of perception, motor skills or consciousness. It may also cause abnormal behaviour. A severe hypoglycaemic event is to be distinguished from mild hypoglycaemic events, the latter with symptoms such as sweating, tremulousness, hunger and tingling around the mouth, which are common occurrences in the life of a person with diabetes treated with insulin and some hypoglycaemic agents.

Potential causes

Hypoglycaemia may be caused by many factors including non-adherence or alteration to medication, unexpected exertion, alcohol intake, or irregular meals. Meal regularity and variability in medication administration may be important considerations for long-distance commercial driving or for drivers operating on shifts. Impairment of consciousness and judgement can develop rapidly and result in loss of control of a vehicle. Excessively tight control may contribute to hypoglycaemia.3

Advice to drivers

The driver should be advised not to drive if a severe hypoglycaemic event is experienced while driving or at any other time, until they have been cleared to drive by the appropriate medical practitioner. The driver should also be advised to take appropriate precautionary steps to help avoid a severe hypoglycaemic event, for example, by:

  • complying with general medical review requirements as requested by their general practitioner or specialist
  • not driving if their blood glucose is at or less than 5 mmol/L
  • not driving for more than two hours without considering having a snack
  • not delaying or missing a main meal
  • self-monitoring blood glucose levels before driving and every two hours during a journey, as reasonably practical
  • carrying adequate glucose in the vehicle for self-treatment
  • treating mild hypoglycaemia if symptoms occur while driving including
  • safely steering the vehicle to the side of the road
  • turning off the engine and removing the keys from the ignition
  • self-treating the low blood glucose
  • checking the blood glucose levels 15 minutes or more after the hypoglycaemia has been treated and ensuring it is above 5 mmol/L (see Patient information)
  • not recommencing driving until feeling well and until at least 30 minutes after the blood glucose is above 5 mmol/L.

Non-driving period after a ‘severe hypoglycaemic event’

If a severe hypoglycaemic event occurs (as defined in section 3.2.1 Hypoglycaemia), the person should not drive for a significant period of time and will need to be urgently assessed. The minimum period of time before returning to drive is generally six weeks because it often takes many weeks for patterns of glucose control and behaviour to be re-established and for any temporary ‘reduced awareness of hypoglycaemia’ to resolve (see below). The non-driving period will depend on factors such as identifying the reason for the episode, the specialist’s opinion and the type of motor vehicle licence. The specialist’s recommendation for return to driving should be based on patient behaviour and objective measures of glycaemic control (documented blood glucose) over a reasonable time interval.

Reduced awareness of hypoglycaemia

Reduced awareness of hypoglycaemia exists when a person does not regularly sense the usual early warning symptoms of mild hypoglycaemia such as sweating, tremulousness, hunger, tingling around the mouth, palpitations and headache. It markedly increases the risk of a severe hypoglycaemic event occurring and is therefore a risk for road safety.4 It may be screened for using the Clarke questionnaire (Figure 9), which may be particularly useful for people with insulin-treated diabetes of longer duration (more than 10 years), or following a severe hypoglycaemic event or after a crash.5,6

When reduced awareness of hypoglycaemia awareness develops in a person who has experienced a severe hypoglycaemic event, it may improve in the subsequent weeks and months if further hypoglycaemia can be avoided.

A person with persistent reduced awareness of hypoglycaemia should be under the regular care of a medical practitioner with expert knowledge in managing diabetes (e.g. an endocrinologist or diabetes specialist), who should be involved in assessing their fitness to drive. As reflected in the standards table, any driver who has a persistent reduced awareness of hypoglycaemia is generally not fit to drive unless their ability to experience early warning symptoms returns or they have an effective management strategy for lack of early warning symptoms. For private drivers, a conditional licence may be considered by the driver licensing authority, taking into account the opinion of an appropriate specialist, the nature and extent of the driving involved and the driver’s self-care behaviours.

In managing reduced awareness of hypoglycaemia, the medical practitioner should focus on aspects of the person’s self-care to minimise a severe hypoglycaemic event occurring while driving, including steps described above (Advice to drivers). In addition, self-care behaviours that help to minimise severe hypoglycaemic events in general should be a major ongoing focus of regular diabetes care. This requires attention by both the medical practitioner and the person with diabetes to diet and exercise approaches, insulin regimens and blood glucose testing protocols.

Figure 9: Clarke hypoglycaemia awareness survey

Note: Units of measure have been converted from mg/dl to mmol/L as per <>