One million drivers are believed to be on the road with a medical condition they haven't let the Driver and Vehicle Licensing Agency (DVLA) know about.

But failing to notify the DVLA of a health issue could see you slapped with a hefty fine of up to £1,000, invalidate your insurance or, even worse, cause an accident.

According to our sister site the Daily Post , the DVLA says you must tell them if you’re suffering with any of the 'notifiable' conditions on its comprehensive list of diseases and ailments.

A DVLA spokesman said: “It is the ongoing legal responsibility of all drivers to ensure that they are medically fit to drive and notify DVLA of the onset or worsening of a medical condition affecting this.

“If patients are unsure whether they need to tell DVLA about a medical condition that could affect their driving, we would strongly encourage them to speak to their doctor or other healthcare professionals.”

There’s a range of unlikely illnesses and conditions that harbour side effects – from hearing loss to sleep deprivation – that might affect your ability to control an automobile, as set out by the motoring experts at Lease Car .

Here is five of the most surprising conditions you might not realise you are required to disclose:

1) Déjà vu

Surprisingly, GOV.UK lists déjà vu as one of the health conditions which could affect your driving.

Whilst most people will regard déjà vu as a common experience in healthy individuals, it is also associated with certain types of epilepsy – this experience of déjà vu is a neurological anomaly related to epileptic electrical discharge in the brain.

It is this medically-induced déjà vu you need to inform the DVLA about.

The Government website states: “You must tell DVLA if you have seizures or epilepsy that cause déjà vu.”

2) Labyrinthitis

Labyrinthitis is a common inner ear infection which causes a delicate structure deep inside your ear (the labyrinth) to become inflamed.

Symptoms can vary in severity - but usually get better after a few weeks.

They can include mild headaches, some hearing loss, ear pain and vertigo.

However, in some cases, the symptoms can last longer and have a significant impact on your ability to carry out everyday tasks.

The Government website states: “You must tell DVLA if you have labyrinthitis.”

3) Sleep apnoea

Sleep apnoea is a relatively common condition where the walls of the throat relax and narrow during sleep, interrupting normal breathing.

This may lead to regularly interrupted sleep, which can have a big impact on your quality of life, increase the risk of developing certain conditions, and even cause you to fall asleep at the wheel - which is incredibly dangerous.

It’s in these severe cases that you should get in contact with your GP/consultant for further advice and consider informing the DVLA.

The Government website states: “You must tell DVLA if you have:

  • Obstructive sleep apnoea which affects your ability to drive safely
  • Obstructive sleep apnoea syndrome

“Ask your doctor if you’re not sure if your obstructive sleep apnoea will affect your driving.”

4) Eating disorders

Having an unhealthy attitude to food doesn’t seem like something that could affect your driving ability straight off the bat, yet there are severe cases that cause horrible side effects - like being weak and dizzy.

The Government website states: “You must tell the DVLA if you suffer from an eating disorder (e.g. anorexia nervosa) and it affects your ability to drive safely. Ask your doctor if you’re not sure if your eating disorder will affect your driving.”

5) Arthritis

Arthritis is a common condition that causes pain and inflammation in a joint, with around 10 million people suffering from it across the UK.

It can affect people of all ages, including children, and as the most commonly affected joints are those in the hands, spine, knees and hips – which obviously you all need full use of to be able to sit in a car and drive safely.

So you should tell the DVLA if your condition affects your driving and has lasted more than three months.

The Government website states: “You must tell DVLA if you use special controls for driving. Talk to your doctor if you’re not sure if your arthritis will affect your driving, or if you must tell DVLA about it.”