If you have diabetes, the main concern when driving is the possibility of having a ‘hypo’ while you are at the wheel, which could cause an accident. You need to be aware of the risks involved and plan in advance before you get behind the wheel.
Key points about diabetes and driving
- Plan to avoid low blood glucose (sugar) while driving.
- Check your blood glucose level before you get in the car. Don’t drive with a blood sugar level under 5mmol/L.
- Carry a blood glucose meter with you when you drive.
- Recheck your blood glucose level at least every 2 hours.
- Travel with fast-acting and longer-acting carbohydrate foods (or drinks), like a muesli bar, banana or fruit juice.
What are the concerns relating to diabetes and driving?
Driving is a complex skill, both physically and mentally. If you have diabetes, you may need to take extra precautions to make sure you are safe on the road.
Hypoglycaemia (low blood glucose)
If you take insulin or some types of diabetes tablets (not metformin), the main risk to your safety is hypoglycaemia (a ‘hypo’), where your blood glucose levels drop too low. This is usually below 4mmol/L but symptoms can occur in some people at blood glucose levels a little above this.
Even mild hypoglycaemia can affect your ability to drive safely. If you don't do anything about it, hypoglycaemia can cause you to pass out (become unconscious).
Hyperglycaemia (high blood glucose)
Very high blood glucose levels (hyperglycaemia) can also make you feel unwell or tired and may affect your ability to drive safely. You should not drive if you’re severely hyperglycaemic.
Other concerns that can affect your ability to drive safely are the possible complications of diabetes, such as eye problems, loss of sensation in your feet and heart problems.
If your diabetes has just been diagnosed and your treatment is still being adjusted, you may not be fit to drive just yet. Check with your healthcare provider, eg, your doctor (GP), a registered nurse or nurse practitioner, or a specialist if appropriate.
Plan to avoid low blood glucose levels while driving
- Check your blood glucose level no longer than 2 hours before driving. It needs to be above 5mmol/L and stable before you drive.
- Always have a meal or snack before you set out on long trips.
- Carry a blood glucose meter with you when you drive.
- Travel with a supply of fast and longer-acting carbohydrate foods (or drinks) such as muesli bars, biscuits, glucose tablets, dried fruit or fruit juice.
- If you are driving for 2 hours or more, recheck your blood glucose level at least every 2 hours to make sure it stays above 5mmol/L.
- Stop to rest and have something to eat and drink regularly if you are on a long trip.
What to do if your blood glucose level gets too low while driving
Many accidents caused by hypoglycaemia are because drivers have kept driving and ignored their hypo warning signs (eg, hunger, sweating, feeling faint). If you feel that your blood glucose is low while driving, take the following steps:
- Stop the vehicle when it’s safe.
- Switch off the engine, remove the keys from the ignition.
- Get out of the driver’s seat.
- Take some fast-acting carbohydrate, such as glucose tablets or sweets, and eat some form of longer-acting carbohydrate, such as a muesli bar or biscuits.
- Check your blood glucose level.
- Don't start driving until 45 minutes after your blood glucose level has returned to normal (above 5 mmol/l).
- It may take up to an hour before your brain has time to recover.
When not to drive
- If you have been recently diagnosed with diabetes and your treatment is still being adjusted, you may not be fit to drive just yet. Check with your doctor or specialist diabetes nurse.
- If you experience hypoglycaemia without warning signs (called hypoglycaemia unawareness), it may be unwise for you to drive. You should discuss this with your doctor or specialist diabetes nurse.
- If you have a severe hypoglycaemic episode (eg, when you need someone else’s help to deal with it), you shouldn’t drive for 24 hours.
- If you have several hypoglycaemic episodes, you should talk to your doctor before you return to driving.
- If you have a severe hypoglycaemic episode while you’re driving, you shouldn’t drive for at least a month – whether you’re involved in a crash or not. You’ll need to talk to your doctor and it’s likely you’ll need to see a specialist before you can safely return to driving.
Sometimes a driver with diabetes may be issued with a licence that has certain conditions attached. The conditions will depend on:
- the type of licence (classes and endorsements)
- how well the diabetes is controlled
- whether you have any history of hypoglycaemic attacks
- how carefully you follow your medicine schedule
- an assessment of the extent to which you suffer from the medical complications that are commonly associated with diabetes.
The NZ Transport Agency decides the licence conditions, with regard to the medical aspects of fitness to drive, and in consultation with the Transport Agency's chief medical advisor.
Insulin and tablets for the control of diabetes are classified as drugs under the Land Transport Act 1998. This means you could be being charged for driving under the influence (of insulin), dangerous driving or driving without due care and attention. You may be prosecuted under this Act if you misuse or abuse medicines and your driving results in crashes or injuries.
For a case to proceed, however, there would need to be proof that the way you had used the medicine was different from how you had been advised to by your doctor.
Passenger services and heavy vehicles
People with type 1 diabetes are generally not considered fit to drive heavy trade vehicles, taxis, buses and other related vehicles. The NZ Transport Agency may, in exceptional circumstances, grant a licence after consultation with your GP and diabetes specialist. If a licence is granted to drive any of these vehicles, strict conditions are likely to be imposed.
The following links provide further information about diabetes and driving. Be aware that websites from other countries may have information that differs from New Zealand recommendations.
Diabetes and driving NZ Transport Agency
Medical aspects of fitness to drive – a guide for health practitioners NZ Transport Agency
|Terrie Spedding is a diabetes clinical nurse specialist working for Health Hawke’s Bay PHO. She has with 30+ years’ experience in all aspects of the care, management and support of people with diabetes, presently working in the primary care sector. She also has an interest in diabetes research.|