Driving after having one too many to drink is obviously banned as well as being on certain prescription drugs.
But, it turns out there's a huge list of health conditions that you must tell the DVLA about and some of them are very common.
And, if you don't tell the DVLA about any of these conditions, then you could be fined up to Â£1,000 and face prosecution if you're involved in an accident.
The DVLA website has added that you must give up your licence if your doctor tells you to stop driving for three months or more.
You also have to do this if you don't meet the required standards for driving because of your medical condition.
Many of us have experienced the strange phenomena of deja vu; a feeling of familiarity and having already lived through something.
It's an unusual and often hard to describe or explain feeling but, if your deja vu is related to a health condition then you must tell the DVLA.
Deja vu is also associated with certain types of epilepsy; a neurological anamoly related to epileptic electrical discharge in the brain.
Suffering from depression is not an uncommon experience; in fact approximately one in four people will experience a mental health problem each year.
In England, one in six people report experiencing a common mental health problem (such as anxiety and depression) in any given week.
However, the DVLA has stated that they must be informed if your depression affects your ability to drive safely.
Obsessive compulsive disorder
Obsessive-compulsive disorder is a mental disorder where people feel the need to check things repeatedly or perform routine tasks repeatedly.
The most common OCD activities include hand washing, counting of things and checking to see if a door is locked.
Once again, the DVLA has stated that if your OCD affects your driving then they must be informed.Sleepiness/sleep apnoea
Many of us have driven to work in the morning after a bad's night sleep, feeling very drowsy and wishing it was the weekend instead.
But some people suffer from medical conditions that cause them to be sleepy during the time they'd normally be awake.
Sleep apnoea is a disorder that stops people breathing repeatedly during their sleep. Both of these conditions must be notified to the DVLA.
Having a bit of an unhealthy attitude to food doesn't seem like something that would affect your driving; most of us love the occasional McDonald's while wishing we were a bit thinner.
But, for some people, an eating disorder can take over your life, make you ill and have a big effect on your driving.
If you've got an eating disorder, such as anorexia nervosa, bulimia or binge eating, and it affects your ability to drive then you must tell the DVLA.