UK Drink Driving Limits at a Glance
- England & Wales — Breath: 35 micrograms of alcohol per 100ml of breath
- England & Wales — Blood: 80 milligrams of alcohol per 100ml of blood
- England & Wales — Urine: 107 milligrams of alcohol per 100ml of urine
- Scotland — Breath: 22 micrograms per 100ml of breath (lower than England & Wales)
- Scotland — Blood: 50 milligrams per 100ml of blood
- Scotland — Urine: 67 milligrams per 100ml of urine
- There is no safe amount to drink before driving — individual tolerance varies significantly.
What Are the Legal Drink Driving Limits in England and Wales?
In England and Wales, the legal limits for driving are set out in section 11 of the Road Traffic Act 1988. There are three prescribed limits, depending on which type of specimen is tested:
- Breath: 35 micrograms (mcg) of alcohol per 100 millilitres (ml) of breath
- Blood: 80 milligrams (mg) of alcohol per 100ml of blood
- Urine: 107 milligrams (mg) of alcohol per 100ml of urine
The breath limit is the most commonly used in practice — the evidential breath testing device at the police station measures the concentration of alcohol in your breath. If your reading is 35mcg/100ml or below, you are within the legal limit. If it is above 35mcg/100ml, you are over the limit and will be charged with drink driving under section 5 of the Road Traffic Act 1988.
What Are the Drink Driving Limits in Scotland?
Scotland introduced lower drink driving limits in December 2014. The Scottish limits are:
- Breath: 22 micrograms of alcohol per 100ml of breath
- Blood: 50 milligrams of alcohol per 100ml of blood
- Urine: 67 milligrams of alcohol per 100ml of urine
The Scottish limits are broadly equivalent to the limits in most other European countries. The lower limit means that even a small amount of alcohol — such as a single unit — could put a driver over the limit in Scotland.
How Many Units Can I Drink Before Driving?
There is no reliable answer to this question — and this is precisely why the advice from road safety organisations and legal professionals is consistent: do not drink and drive at all.
The rate at which your body processes alcohol depends on a wide range of individual factors, including your weight, sex, age, metabolism, whether you have eaten, and your general health. Two people of the same weight can drink the same amount and have very different breath readings. There is no formula that reliably tells you how many units you can drink and remain under the legal limit.
As a very rough guide, the NHS suggests that one unit of alcohol takes approximately one hour to leave your body. However, this is an average — for some people it takes longer, and alcohol consumed the night before can still be in your system the following morning.
Morning After Drink Driving
One of the most common scenarios we see is clients who are stopped and tested the morning after a night of drinking. Many people assume that sleeping off alcohol means they are safe to drive — but this is not always the case.
If you consumed a significant amount of alcohol the previous evening, you may still be over the legal limit the following morning. The only way to know for certain is to use a personal breathalyser — but even these are not always accurate. The safest approach is to avoid driving if you have been drinking.
What Is the Prosecution Limit?
In England and Wales, there is a statutory concession that applies to breath readings between 36mcg/100ml and 39mcg/100ml. If your breath reading falls in this range, you have the right to request a blood or urine test instead. This is because the evidential breath testing device has a margin of error, and the law recognises that a reading in this range may not reliably indicate that you are over the limit.
If your reading is 40mcg/100ml or above, the prosecution will proceed on the basis of the breath reading alone. You do not have the right to request a blood or urine test at this level.
What Happens If You Are Over the Limit?
If your breath, blood, or urine reading exceeds the prescribed limit, you will be charged with drink driving under section 5 of the Road Traffic Act 1988. The penalties on conviction are:
- Mandatory minimum 12-month driving ban (3 years for a second offence within 10 years)
- Up to 6 months imprisonment
- Unlimited fine
- Criminal record lasting 11 years on your driving licence
- New drivers: licence revoked and must retake test
The level of alcohol above the limit is a significant factor in sentencing. A reading just above the limit may result in a shorter ban and a lower fine, while a very high reading — particularly if combined with aggravating factors such as an accident or a child in the vehicle — will result in a longer ban and a higher fine.
Can I Challenge a Drink Driving Charge?
Yes. There are a number of potential defences and challenges available in drink driving cases, including: procedural errors by the police; the hip flask defence (alcohol consumed after driving but before testing); faulty or uncalibrated equipment; medical reasons; and special reasons arguments that may prevent a ban even on conviction.
If you have been charged with drink driving, contact our specialist road traffic solicitors as soon as possible. The sooner you get advice, the more options you have.