Diabetes and driving: DVLA rules, hypo safety and your licence

Diabetes UK identifies three main ways diabetes can affect driving safely. The first is having treatment that puts you at risk of a hypo, where blood glucose drops below 4 mmol/l. The second is not being able to recognise the warning symptoms of a hypo, known as hypo unawareness. The third is developing complications such as retinopathy or neuropathy that make driving harder.

Hypos mainly affect people on insulin and on certain tablets such as sulphonylureas, Diabetes UK explains, and some can be severe enough that you need help to treat them. If you are unsure whether your treatment carries this risk, ask your healthcare team. The rules differ by vehicle: Group 1 covers cars and motorbikes, and Group 2 covers lorries and larger vehicles, with more complicated requirements for the latter.

The rules come from the DVLA in England, Scotland and Wales and from the Driver and Vehicle Agency in Northern Ireland. GOV.UK states that you can be fined if you do not tell the DVLA about a medical condition that affects your driving, and may be prosecuted if you are involved in an accident as a result.

GOV.UK sets out different duties depending on how your diabetes is treated. The table below summarises its position for car and motorbike licences, and it is a summary rather than a substitute for the official forms and leaflets.

• GOV.UK says bus, coach or lorry drivers on insulin must stop driving and tell the DVLA when they start insulin, and that DVLA will say when they can drive again.

• For a bus, coach or lorry licence, GOV.UK says you must also tell DVLA if your diabetes is treated by tablets or non-insulin injections. Diet-only treatment does not need reporting.

The DVLA guidance for medical professionals defines adequate awareness of hypoglycaemia as being able to recognise symptoms in time to safely stop the vehicle. For insulin-treated Group 1 drivers, licensing requires adequate awareness, no more than one episode of severe hypoglycaemia while awake in the preceding 12 months and the latest more than 3 months ago, appropriate glucose monitoring, meeting visual standards, no disqualifying complications and regular medical review.

Severe hypoglycaemia is defined in law as an episode requiring the assistance of another person. The DVLA guidance says that, for Group 1 drivers, an episode during established sleep is no longer considered relevant for licensing unless there are concerns about the ability to recognise low glucose, whereas Group 2 drivers must report all severe episodes including those in sleep.

Diabetes UK adds that you do not need to tell the DVLA about a hypo you managed yourself, only a severe hypo where you needed help.

If you usually check your blood glucose, Diabetes UK says you must follow the rules about when: just before driving, however short the trip, and on longer journeys at least every two hours, with no more than two hours between checks. Its checklist for people at risk of hypos adds keeping spare test strips and your meter in the car, keeping hypo treatments within easy reach, taking breaks on long journeys and not delaying meals or snacks.

Its "five to drive" guidance says glucose needs to be 5 mmol/l or above before you set off. Between 4 and 5, eat some carbohydrate before heading out. Under 4, treat the hypo and check your level again before driving.

Continuous glucose monitors can be used for the checks. DVLA guidance says drivers should use a device approved for non-adjunctive use, meaning one approved for treatment decisions based on its readings, and must carry a finger-prick meter as a back-up in case the sensor fails or the reading does not match how they feel. It also says sensor alarms should supplement, not replace, your own awareness, should be set above 4.0 mmol/l while driving, and that anyone who becomes dependent on alarms to recognise a low must stop driving and notify the DVLA.

Diabetes UK states that it is the law that you must stop. Find somewhere safe to pull in as soon as possible, switch off the engine, take the keys out and move out of the driver's seat, because otherwise police can treat you as still in charge of the vehicle and you could be prosecuted.

Take fast-acting carbohydrate such as glucose tablets or sweets, followed by something longer-acting such as plain biscuits or crackers. Do not drive until 45 minutes after your glucose has returned to 5 mmol/l or above, which Diabetes UK says is the time it takes for concentration to recover. If you are struggling with hypos, talk to your healthcare team about whether you should be driving.

Diabetes UK says that if you start having problems with your eyes you need to let the DVLA know and you may need a special eye test for driving at a DVLA-recommended optician, paid for by the DVLA. Some eye problems are treated successfully, so you can reapply for your licence. GOV.UK separately lists diabetic retinopathy with laser treatment among the eye conditions that must be reported, and notes the standard of reading a number plate at 20 metres.

Neuropathy can cause loss of feeling in the hands and feet. If it is severe, Diabetes UK advises asking your healthcare team or the DVLA, and says that if neuropathy or an amputation means you need an adapted vehicle you must apply to the DVLA for an adapted vehicle licence. Heart problems, sleep apnoea and stroke can also affect fitness to drive and may need reporting.

Diabetes UK says that if a licence is revoked you can nearly always reapply after some time, most commonly after severe hypos, and you can apply for a new licence up to eight weeks before the date given on a refusal notice. What happens next depends on why it was taken away.

You must declare diabetes as a material fact when applying for car insurance, according to Diabetes UK, which adds that most insurers will not charge more because of diabetes and that you should complain if they do. People who drive for work may worry about licence changes, and Diabetes UK offers information on your rights.

Your GP, practice nurse or diabetes team on the NHS is the first source for working out which category you fall into and what to tell the DVLA. They can also review hypo risk, adjust treatment and arrange eye checks.

Private diabetes specialists can provide a second opinion on hypo risk, treatment changes or technology such as glucose sensors, and can write supporting letters. The duty to notify the DVLA stays with you either way, and the licensing decision is made by the DVLA, not by the clinic.