Is there a police test for drug driving?

Police Officers can carry out field impairment tests (FITs) at the roadside to help ascertain whether the driver is unfit to drive because of drugs.

What does the test involve?

The FIT includes five exercises that aim to show if the driver is impaired, and whether that impairment may be through drugs:

Pupillary test

The driver’s eyes are checked to assess their pupils’ size, condition and reaction to light. Drugs such as heroin will make the pupils constrict (get smaller), while speed or cocaine can make them dilate (get bigger).

Romberg test

The driver is asked to stand with their head tilted slightly back, with their eyes closed, and state when 30 seconds has passed. This helps the officer assess balance and judgement of time. Stating that 30 seconds has elapsed too quickly or too slowly may be a sign of drug use. If the person is under the influence of drugs or alcohol, they might also sway or raise their head or arms.

Walk and turn test

The driver is asked to walk heel-to-toe along a straight line, while counting their steps out loud and looking at their feet. Police will be looking for signs such as losing balance, tripping, missing the heel or toe, stepping off the line or not turning as instructed.

One leg stand test

The driver is asked to stand on one leg while counting out loud. Police will look for swaying, loss of balance or not following the instructions.

Finger to nose test

The driver is asked to touch their nose with one finger, while tilting their head back and closing their eyes. The police officer will tell them which hand to use. This is a test of depth perception.

What happens if I fail the FIT?

The exercises cannot be "passed" or "failed", but they can be performed well or poorly, which helps the officer to decide the person’s condition and whether they should be arrested for driving while unfit due to drugs. At the police station, the driver may be required to provide a specimen of blood or urine, which will be tested for drugs in a laboratory.

What about medicines?

A "medical defence" applies to the new offence of driving while in excess of a specified drug limit, and not to the offence of impaired driving. 

If a driver tests positive for certain specified prescribed drugs, but they have been taken in accordance with instructions given by a healthcare professional or the information leaflet that comes with the medicine, then a "medical defence" may be claimed.

It is advised that a driver using certain specified prescribed drugs carries some sort of evidence to show the medicine is prescribed or taken correctly, even if it’s an over-the-counter medicine.

The "medical defence" only applies to the offence of having a specified drug above the limit and not to driving while unfit through drink or drugs. Some prescription drugs and over-the-counter medicines can have an effect on the skills needed to drive safely, including drowsiness; if the driver is impaired, prosecution is still possible.

It is an offence to drive or attempt to drive while unfit through drugs, and the law does not distinguish between illegal drugs and prescribed medicines.

Penalties for drug driving

If you’re convicted of drug driving you’ll get:

  • a minimum one-year driving ban
  • a fine of up to £5,000, up to six months in prison, or both
  • a criminal record

Your driving licence will also show that you’ve been convicted for drug driving. This will last for 11 years.

For more information about the effects of drugs and alcohol on driving, see:

Read the answers to common health questions about alcohol, drugs and smoking.

Further information:

Page last reviewed: 28/08/2014

Next review due: 27/08/2016