Under UK law a motorist can have a small amount of alcohol in their system, but the only safe option is to avoid drinking completely before getting behind the wheel. Learn more about current UK limits.


Driving while under the influence of drink can cause a number of physical and mental side effects which can impair a person's ability to safely control their vehicle. With an increased likelihood of a collision, the chance of causing death or injury to themselves, their passengers, or other road users, also increases. 


So, what is the legal limit for alcohol when driving?


Alcohol limit: UK driving


In England, Wales, and Northern Ireland, the drink-driving limit is 80 milligrams of alcohol per 100 millilitres of blood, 35 micrograms of alcohol per 100 millilitres of breath, or 107 milligrams of alcohol per 100 millilitres of urine.


In Scotland the limit is stricter, at 50 milligrams of alcohol per 100 millilitres of blood, and 22 micrograms of alcohol per 100 millilitres of breath, or 67 milligrams per 100 millilitres of urine.


How do we compare to other European countries?


The Northern Ireland, Wales and England drink drive limit is actually lenient by European standards. Most of Western Europe, including Scotland, has a 50mg/100ml of blood limit. Drink drive limits tend to be even stricter in Eastern Europe. Armenia and Azerbaijan (among others) do not permit people to have any alcohol in their system when behind the wheel.




How many units to drive?


It may be unwise to decide what a safe level of alcohol is by the number of units consumed, not least because approaching the limit carries the risk of overstepping it. As the Metropolitan Police website states, "If you’re driving, don’t drink any alcohol at all."


However, the question - How many units can you drink and drive? - is a common one. For a man, around 4 units of alcohol (about the same as two pints of normal strength lager) would reach the limit, while for a woman just over a pint of normal strength lager or a large glass of wine would put them at the limit.


How alcohol impacts a person can vary due to factors such as:

  • Age
  • Gender
  • Tolerance (or reverse tolerance) to alcohol
  • Body composition/weight
  • Liver condition 
  • Dehydration
  • Fatigue
  • Medication
  • Carbonation 


How long after drinking can you drive?


How soon it is safe to drive depends on a number of factors, including how quickly you drank the alcohol, how much you drank, your age, weight, and gender. It’s clear that there is no one-size-fits-all time period. 


However, according to Drinkaware.co.uk, which is partly government founded, "On average, alcohol is removed from the body at the rate of about one unit an hour." It also states that "The only way to eliminate alcohol from the body is to let time pass."


In short, alcohol can stay in your system for up to 24 hours, by which time it should be safe to drive.


However, if you've only had a small amount of alcohol, you'll be able to drive sooner. 


That said, it's best to avoid alcohol altogether if you plan to drive in the very near future.




Penalties for drunk driving


If a person is found by the police to have exceeded the drink drive limit, they may face:

  • a criminal record
  • up to six months in prison
  • a fine (unlimited)
  • an automatic driving ban of at least one year (this rises to three years if you have been convicted twice in the previous 10 years)


The same penalties apply if a person is caught behind the wheel while impaired by certain drugs (which can include prescription medication as well as illegal substances).


A person found to be drink or drug driving may also experience:

  • increased insurance costs
  • endorsement of their driving licence for 11 years
  • their employer finding out they have a driving conviction
  • difficulty entering some countries - notably the United States


Penalties for causing death by drunk/drug driving


Causing death by careless driving while under the influence of drink or drugs can lead to:

  • Life imprisonment (maximum) if the offence was committed on or after 28 June 2022)
  • 14 years imprisonment (maximum) if the offence was committed before 28 June 2022).




How are the UK’s drink driving laws enforced?


Police can pull over any driver they suspect of being under the influence of alcohol (or drugs). For example, they may be driving erratically, or may have been involved in a collision.


Officers can then require the driver to take an alcohol breath test (to be “breathalysed”), and can arrest the driver if they fail to comply. 


If a driver fails a breath test, they will be taken to a police station for a final breath test. If they fail a second time, they will be charged.


If a driver cannot undertake a breath test for medical reasons, they may be required to take a blood test. Test results for a blood test can take between 24 hours to several weeks, so agreeing to being breath-tested may be the least stressful option - particularly since both are likely to deliver the same result (positive or negative).


Officers may also check a driver’s balance by asking them to walk in a straight line. However this is not considered hard evidence, since people may be unable to walk straight for medical reasons or due to fatigue, for instance.