Medications That Affect Driving in the UK

If you take a medicine, the practical question is whether it affects your ability to drive safely. Medicines can cause effects such as sleepiness or tiredness, and a prescription does not automatically make driving safe or lawful. If you feel unfit to drive, do not drive. If you are uncertain about a particular medicine, ask your pharmacist, doctor or another healthcare professional before driving, and follow their advice on how to take it.

How medicines can affect driving

Some medicines can affect alertness or cause other effects that matter when you are behind the wheel. The examples supported by the sources for this guide are codeine and cetirizine. They do not establish that every medicine in a broader category has the same effect, or tell you how a medicine will affect you personally.

The NHS says codeine can cause sleepiness or tiredness. Its advice is not to drive, ride a bike or use machinery if you feel sleepy or tired after taking codeine, until those symptoms have gone. NHS guidance describes cetirizine as a non-drowsy antihistamine, but says it can still make some people sleepy. If that happens, do not drive until you no longer feel tired. Read the leaflet supplied with your own medicine and seek advice if you are unsure.

Do not stop, change or skip prescribed treatment to try to make driving safe. Ask the prescriber or pharmacist what to do if a medicine is affecting you. They can consider the medicine and your circumstances; this guide cannot provide a personal clearance or a fixed waiting time.

What UK drug-driving law says

In England, Scotland and Wales, it is illegal to drive if you are unfit to do so because of legal or illegal drugs. Legal drugs include prescription and over-the-counter medicines. The GOV.UK guidance on drugs and drivingGOV.UK advises you to speak to a doctor, pharmacist or healthcare professional if you are taking legal drugs and are not sure whether you should drive.

The law also sets specified blood limits for certain drugs. The rules distinguish between those drugs taken without a prescription and medicines prescribed to you. For the medicines listed in the guidance, you can drive above a specified limit only if both conditions apply: a healthcare professional prescribed the medicine and you followed their advice on how to take it, and the medicine is not making you unfit to drive. A prescription is not a defence to impairment. These are separate questions: whether you are fit to drive, and whether the specified-limit offence applies.

The GOV.UK page names medicines including diazepam, lorazepam, methadone, morphine and opioid-based medicines such as codeine, tramadol and fentanyl. It also lists several other medicines. Use the current page for the full list and legal detail, rather than relying on a remembered list. The guidance states that this law does not cover Northern Ireland, although a person who is unfit to drive there could still be arrested.

Does taking medicine mean you must tell DVLA?

This is different from the immediate decision about whether you can safely drive. The DVLA guidance says licence holders have a legal duty to notify DVLA of an injury or illness likely to affect safe driving, subject to the guidance’s exceptions for some short-term conditions. It also says drivers should follow prescribed treatment and comply with the requirements of their licence.

That does not establish a general rule to report every prescription. Whether a condition or treatment needs to be reported depends on the circumstances and the relevant DVLA rules. Check the current guidance on medical conditions, disabilities and drivingGOV.UK and the detailed DVLA guidance on assessing fitness to driveGOV.UK. If you are unsure whether your condition or treatment is relevant, ask your doctor or pharmacist.

DVLA, rather than an appointment at a medical practice, makes licensing decisions. The general DVLA guidance describes Group 1 as cars and motorcycles, and Group 2 as large lorries and buses. It says that, in most cases, Group 2 medical standards are substantially higher. A doctor completing a medical form does not decide whether DVLA will issue or retain your licence.

A useful question to ask your pharmacist

Bring the medicine packaging or a current medicines list, and explain what you drive and when you need to drive. You could ask:

“I drive for work and take [medicine name] at [the time I take it]. Could it affect my alertness or make me unfit to drive, what effects should make me stop driving, and what should I do if I notice them?”

Tell the pharmacist about other medicines, remedies or supplements you take. The NHS codeine guidance specifically advises telling your doctor about other medicines, herbal remedies, vitamins or supplements before taking codeine. A pharmacist can help explain the leaflet and suggest whether you should contact the prescriber. Do not ask for a generic waiting period: the sources here do not provide one that applies to everyone.

If you feel affected before a shift

If you feel sleepy, tired or otherwise unfit to drive, do not set off. Contact your pharmacist, prescriber or healthcare professional for advice about the medicine and your next steps. If you drive for an employer, check the relevant workplace process as well. Employer rules and drug-testing processes are separate from DVLA licensing and do not establish that you are safe or legally entitled to drive.

If you have taken more codeine than prescribed, NHS guidance says to call NHS 111 for advice. If you are told to go to A&E, do not drive there; ask someone to take you or call 999 for an ambulance. For other urgent or severe symptoms, use the appropriate urgent NHS service.

Driver medical appointments

If you are preparing for an HGV, LGV or PCV medical, bring an accurate list of your medicines and be ready to discuss relevant health information. The appointment can record information for the medical assessment, but it cannot give you personal permission to drive while affected by medicine or replace the DVLA’s licensing decision. Taxi medical requirements may also include standards set by your local council, so check what your licensing authority requires.

Our Medical Team

Driver medical appointments

South Wales Driver Medicals offers driver medical appointments for HGV, PCV, LGV and taxi drivers. Contact the clinic for information about the clinician conducting your appointment and the requirements for your form.

If you need an appointment, see our HGV, LGV and PCV medical service or taxi medical service. You can also contact SWDM with a question about which service to choose.

Sources

Sources

1. gov.ukDrugs and driving: the law(accessed 2026-10-13)
2. dvlaGeneral information: assessing fitness to drive(accessed 2026-10-13)
3. nhsCodeine(accessed 2026-10-13)
4. nhsCommon questions about cetirizine(accessed 2026-10-13)