Current UK Drink Driving Limits
Breath Alcohol Limit
The legal breath alcohol limit in England and Wales is 35 micrograms of alcohol per 100 millilitres of breath. This is the limit used at the police station when the evidential breath test is administered on an approved device such as the Intoxilyser EC/IR.
In Scotland, the limit was lowered in December 2014 to 22 micrograms of alcohol per 100 millilitres of breath. This is the lowest breath alcohol limit in the United Kingdom.
Blood Alcohol Limit
The legal blood alcohol limit in England and Wales is 80 milligrams of alcohol per 100 millilitres of blood. Blood tests are used when breath testing equipment is unavailable, when a medical condition prevents a breath test, or when the statutory option is exercised.
In Scotland, the blood alcohol limit is 50 milligrams of alcohol per 100 millilitres of blood. This lower limit means that Scottish drivers can be prosecuted at a level that would be legal in England and Wales.
Urine Alcohol Limit
The legal urine alcohol limit in England and Wales is 107 milligrams of alcohol per 100 millilitres of urine. Urine samples are taken in limited circumstances, typically when neither a breath nor blood sample can be obtained.
In Scotland, the urine alcohol limit is 67 milligrams of alcohol per 100 millilitres of urine. The decision to request a urine sample is made by the police at the station when other methods are not possible.
How the Limits Are Measured
At the roadside, police use a preliminary breath test device to screen for alcohol. This screening test is not evidential and cannot be used in court. Its purpose is to give the officer reasonable cause to arrest and require a formal test at the police station.
At the police station, the evidential breath test is conducted on an approved device. The device takes two breath samples and the lower of the two readings is used as the evidential result. If the lower reading is between 40 and 50 micrograms, the driver has the right to request a replacement blood or urine test under the statutory option.
Blood and urine samples are analysed in a forensic laboratory. The sample is split, and the driver is entitled to have their portion independently analysed. Results must be obtained using approved methods and the chain of custody must be maintained throughout.
Are the Limits Different in Scotland?
Yes. Scotland reduced its drink driving limits on 5 December 2014 under the Road Traffic Act 1988 (Prescribed Limit) (Scotland) Regulations 2014. The breath limit fell from 35 to 22 micrograms per 100 millilitres of breath. The blood limit fell from 80 to 50 milligrams per 100 millilitres of blood.
This means that a driver who would be legal in England and Wales could be over the limit in Scotland. If you regularly drive across the border, the Scottish limit applies whenever you are driving on Scottish roads. The penalties for drink driving in Scotland are the same as in England and Wales.
How Much Can You Drink and Stay Under the Limit?
There is no safe number of drinks that guarantees you will remain under the legal limit. Alcohol affects individuals differently based on weight, sex, age, metabolism, food intake and general health. Two people drinking the same amount can produce very different breath alcohol readings.
As a rough guide, one unit of alcohol raises blood alcohol by approximately 15 to 20 milligrams per 100 millilitres of blood for an average adult. A pint of ordinary strength beer contains approximately 2 units and a large glass of wine approximately 3 units. However, these figures vary widely and should not be relied upon.
The only guaranteed way to be under the limit is to not drink any alcohol before driving. Government advice is clear: if you plan to drive, do not drink at all.
What Happens If You Are Over the Limit?
If the evidential test confirms you are over the prescribed limit, you will be charged with driving or attempting to drive with excess alcohol contrary to section 5(1)(a) of the Road Traffic Act 1988. You will be given a charge sheet and bailed to appear at the magistrates court.
The offence carries a mandatory minimum 12-month driving ban, an unlimited fine and up to 6 months' imprisonment. The actual sentence depends on how far over the limit you were and any aggravating or mitigating factors. You will also receive a criminal record and 3 to 11 penalty points on your driving licence.