Hypoglycaemia and driving

When driving, one of the most important things to consider is the risk of hypoglycaemia. The current guidlines from the DVLA are:

you should not drive if you feel hypoglycaemic or if when testing your blood glucose it is less than 4mmol/l.
If hypoglycaemia develops when driving you should stop the vehicle as soon as possible in a safe location, switch off the engine, remove the keys from the ignition and move into the passenger seat. Then treat your hypo.
Do not resume driving until 45 minutes after the blood glucose has returned to normal. It takes up to 45 minutes for the brain to fully recover.
Always keep an emergency supply of fast-acting carbohydrate such as glucose tablets or sweets within easy reach inside the vehicle.
Carry your blood glucose meter and blood glucose test strips with you. Check your blood glucose before driving (even on short journeys) and test regularly (every two hours) on long journeys. If blood glucose is 5mmol/l or less, take a snack before driving.
Carry personal identification indicating that you have diabetes in case of injury in a road traffic accident.
Particular care should be taken during changes in insulin regimens, changes in lifestyle, exercise, travel and pregnancy.
Take regular meals, snacks and rest periods on long journeys. Always avoid alcohol.

Taken from DVLA: At a glance: guide to the current Medical Standards of Fitness to Drive, updated September 2009.