Your health on the road

Alcohol, illegal drugs, medicines, injuries, tiredness and your mood can all affect your driving. If you ever feel that you might not be able to drive safely, do not drive. Decide the best way to deal with the situation: you may need to delay your journey or find a different way to make your journey. If it’s a longer-term problem, you may have to stop driving altogether.


You must not drink and drive. Alcohol will seriously affect your judgement and ability to drive safely.

In 2015, 200 people were killed in drink-drive accidents and 1,170 people were seriously injured. Statistics for the following year (2016) show that drivers and riders aged 20 to 29 failed more breath tests than any other age group. (Source: Dept for Transport/National Statistics).

The amount of alcohol (units) in different types of drink varies. In England and Wales, you must not drive if your breath alcohol level is higher than 35 microgrammes per 100 millilitres (which is the same as a blood alcohol level of 80 milligrammes per 100 millilitres). In Scotland, the legal limits are lower: a breath alcohol level of 22 microgrammes per 100 millilitres, or a blood alcohol level of 50 milligrammes per 100 millilitres. Driving with alcohol in your blood is extremely dangerous and carries serious penalties if you drive or attempt to drive while over the legal limit. You can find more information on penalties in The Highway Code (GOV.UK).

If you’re not sure whether you’re over the limit, do not drive.

It’s safest not to drink any alcohol before you drive. For more information on drinking and driving, see GOV.UK.

Any amount of alcohol can affect your judgement of speed, distance and risk; it can also make you sleepy. It takes just over an hour for your body to process a unit of alcohol and remove it from your system so if you drink heavily in the evening, you may still be over the limit the following day.

Drugs, medicines and driving

If you’ve taken illegal drugs, it’s against the law for you to drive. See GOV.UK for more on the tests and penalties for drug-driving.

The effects of illegal drugs can be even more serious than alcohol. Drugs can have unpredictable effects and you may not be aware of them affecting you. The direct effects of some drugs can last up to 72 hours.

During 2011, at least 640 accidents were caused by drug-drivers (using illegal drugs or medicines), including 49 deaths (source: Department of Transport).

Some medicines can make you sleepy and will affect your ability to drive. Whether you’ve bought the medicine over the counter or been given it on prescription, always read the label. If it says ‘may cause drowsiness’, it probably will make you sleepy. If you’re not sure whether it’s safe to drive while taking a medicine, check with your doctor or pharmacist.

Taking a combination of prescription medicines, over-the-counter medicines, illegal drugs, controlled drugs or alcohol can have an unpredictable effect on you, so you should not drive while you could be affected by them.

Driving when you’re tired

If you’re tired, you will not be fully alert and aware of what’s going on around you, which means that you will not be able to drive safely. Do not begin a journey if you feel tired.

If you start to feel tired while you’re driving

  • find somewhere safe to stop so you can rest (never on a motorway hard shoulder)
  • try having a caffeine drink and a short nap to refresh you before you start driving again
  • open a window to let in some fresh air if you cannot stop immediately.

To help you stay alert, make sure you

  • have the driving seat in the right place so that you can use the pedals, gear stick and steering wheel comfortably
  • sit up straight – if you slouch, you will not breathe in as deeply as you should.

Driving with an injury

You must make sure that you have full control of your vehicle at all times.

For example

  • a twisted ankle can affect how you use the pedals
  • a stiff neck can make it difficult to check mirrors and blind spots.

If you’ve suffered an injury, you may want to check with your doctor before you drive. Think before you drive: if you cannot control the car properly and see all around, you will not be able to drive safely.


To have a driving licence, you must be able to read in good daylight, with glasses or contact lenses if necessary, a vehicle number plate from a distance of 20 metres (about 5 car lengths). If you need glasses or contact lenses to do this, you must wear them whenever you’re driving.

Eyesight changes over time so you must have an eyesight test at least every 2 years. If you drive when your eyesight does not meet the standard, you’ll be driving illegally and you’ll be less safe on the road.

When the sun is bright, use sunglasses to reduce glare, which can make your eyes tired and reduce the amount you can see. Make sure you take them off when you drive through a tunnel or when conditions are less bright so you can still see clearly.

Medical conditions that affect your driving

Some health conditions can make it unsafe for you to drive and you may need to give up your licence. Check which medical conditions you need to tell DVLA about.

If you’re not allowed to drive anymore, find out how to give up your driving licence for medical reasons.

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