After a spate of celebrity arrests for drink driving including Wayne Rooney and Kirsty Gallagher, it is a question that we are increasingly frequently asked. How much alcohol is safe to drink before driving?

What is the UK Drink Driving Limit?

The drink driving limit differs depending on whether you are in England, Wales, Northern Ireland or Scotland.

The limit in England, Wales and Northern Ireland is 80 milligrammes of alcohol per 100 mls of blood. This equates to 35 micrograms per 100 mls of breath or if a urine sample is given the limit is 107 milligrammes of alcohol per 100 mls of urine.

In Scotland the alcohol limits are lower and are 50 milligrammes of alcohol per 100 mls of blood. The breath limit is 22 micrograms of alcohol per 100 mls of breath or 67 milligrammes per 100 mls of urine.

How many units of alcohol are in a glass of wine or a pine of beer?

The size and strength of your drink is determined by the number of units that you are drinking. As an example, wine comes in different strengths and also different sizes. There are generally three different pub measures of wine being a small glass (125 mls) a medium glass (175 mls) and a large glass (250 mls).  Wine also comes in different strengths ranging generally between 11% ABV and 14% ABV.  Therefore there can be a big difference between the number of units of alcohol in a glass of wine. A small glass of 11% wine might only contain 1.4 units whereas a large glass of 14% wine may contain 3.5 units.

Similarly lager and beer come in different strengths and the strength of the lager will affect the number of units of alcohol contained within it. A pint of strong lager could contain more than 3 units of alcohol.

How many units of alcohol can you drink before driving?

It is not possible to accurately determine how many units of alcohol one can consume before driving as you cannot easily convert the drink drive limit into units of alcohol. 

There are a number of different factors that can impact how alcohol is absorbed into your blood which can place you over the drink drive limit.

Such factors can include:

  • Your weight
  • Your age
  • Your sex
  • Your metabolic rate
  • What food you have eaten recently
  • The type of alcohol you are drinking
  • The amount of alcohol you are drinking
  • Any medication you may be taking

It could take two hours for a pint of lager to leave your system and potentially even four hours for a large glass of wine to leave your system. In addition to the amount of time for the alcohol to leave your system you also need to allow time for the alcohol to be absorbed into the system.

It is too difficult to predict how long it would take after having consumed alcohol for you to be under the drink drive limit due to the individual factors that contribute to how your body processes alcohol.

The easiest way to avoid being over the drink driving limit is to not drive when you are drinking alcohol and to have ‘none for the road’.

What about the ‘morning after’?

Again, as everybody deals with alcohol differently and processes alcohol at different timescales, it is impossible to say when you will be safe to drive the next day if you have had a heavy night of drinking the night before. If you are going to be consuming a large amount of alcohol during an evening we would always suggest that you do not drive the next day and enjoy the opportunity to relax instead.

Ruth Peters – Specialist Motoring Lawyer

Written by Ruth Peters, Specialist Motoring Solicitor at Olliers Solicitors Motor Law. If you require further advice in relation to an offence of drink driving (or indeed any other motoring offence) please contact Ruth on 0808 168 0017. You can also email Ruth at [email protected] or click here to contact us.

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