The number of alcohol units one can drink and still legally drive varies and depends on many factors, including gender, weight, metabolism, and the type of alcohol consumed. In the UK, the legal drink driving limits relate to the concentration of alcohol in the blood, breath, or urine:
- In England, Wales, and Northern Ireland:
- Blood: 80 milligrams per 100 ml
- Breath: 35 micrograms per 100 ml
- Urine: 107 milligrams per 100 ml
- In Scotland (stricter limits):
- Blood: 50 milligrams per 100 ml
- Breath: 22 micrograms per 100 ml
- Urine: 67 milligrams per 100 ml
The Department for Transport recommends no more than 2 to 3 units of alcohol for men and 1 to 2 units for women if driving, but the safest option is to avoid alcohol entirely before driving. One unit of alcohol is defined as 8 grams or 10 ml of pure alcohol. Examples of units in common drinks:
- A pint of 3.8% ABV lager contains about 2.2 units
- A 250 ml glass of 11% ABV wine contains about 2.8 units
- A single 25 ml shot of spirits is 1 unit
Because many factors influence alcohol metabolism, even small amounts can impair driving, and what keeps one person under the limit may push another over it. Therefore, it is impossible to specify a safe number of units to drink before driving for everyone.
