How to find and join a clinical trial in the UK, US or Europe

Thousands of clinical trials are recruiting at any one time, many of them looking for people with common conditions as well as rare ones. Finding one that fits you can still feel hard. Registries are written for researchers, eligibility rules are long, and it is not always clear who to ask.

This guide explains where to search, how to read a trial listing, how to judge whether a study suits you, what to ask before you agree, and what your rights are once you take part. It covers the UK, the US and the EU, where most of our readers are.

This guide is for general information and is not medical advice. Please talk to your own doctor before joining a trial or changing any treatment.

Start with your own doctor

The simplest route into a trial is often your specialist or GP. Hospital teams know which studies are open locally and can check your records against the entry criteria. In the UK, many NHS trusts have research nurses whose job is to help patients find studies.

It is reasonable to ask at any appointment: "Are there any clinical trials I might be suitable for?" Doctors will not be offended. Research is part of NHS care, and the NHS Constitution commits the health service to letting patients know about research they may be eligible for.

Where to search yourself

Several free public databases list trials:

• ClinicalTrials.gov, run by the US National Library of Medicine, is the largest registry in the world and includes many UK and European studies.
• Be Part of Research, run by the UK National Institute for Health and Care Research (NIHR), lists studies recruiting in the UK and lets you search by condition and postcode.
• The ISRCTN registry holds many UK academic trials.
• The EU's Clinical Trials Information System public portal lists trials authorised under the EU Clinical Trials Regulation.
• The World Health Organization's International Clinical Trials Registry Platform searches registries from many countries at once.

Charities often run their own trial finders. Cancer Research UK, for example, has a searchable database of UK cancer trials written in plain English. Patient groups for rare diseases frequently know about studies before they are widely advertised.

How to search well

Registries respond best to precise terms. Try:

• the formal name of your condition, plus any common alternatives
• the stage or type of disease, if relevant
• your country or town
• the status filter set to "recruiting" or "not yet recruiting"

If you know the name of a drug you are interested in, search for that too. Every registered trial has an identifier, such as NCT04437654 on ClinicalTrials.gov, which makes it easy to find the same study elsewhere or to ask your doctor about it.

How to read a trial listing

A registry entry follows a standard layout. The parts most worth reading are these.

Brief summary. What the trial is testing and why, in a few sentences.

Phase. Phase 1 trials test safety and dosing and are usually small. Phase 2 trials look for early signs of benefit. Phase 3 trials compare a new treatment with placebo or existing care in larger groups. Phase 4 studies follow medicines already on the market.

Design. Whether people are randomised, whether there is a placebo, and whether the trial is blinded. Our guides on placebo and blinding and open-label versus blinded trials explain what those terms mean for you.

Eligibility criteria. The inclusion criteria say who can join. The exclusion criteria say who cannot. Age limits, disease stage, previous treatments and other health conditions are common factors.

Locations and contacts. Where the trial is running and who to contact. Some listings give a central phone number or email for enquiries.

Outcomes. What the trial will measure. This tells you what the researchers hope to change.

Why eligibility rules exist

Eligibility criteria can feel frustrating, especially when you are keen to try something new. They exist for two reasons: to protect people for whom the treatment might be unsafe, and to make sure the trial can answer its question clearly.

Rules are slowly becoming less strict in many areas, as regulators encourage trials that include older people, people with other conditions, and a more diverse mix of participants. If you are close to the limits, it is still worth asking. The study team makes the final decision after screening.

Questions to ask before you agree

Once you find a possible trial, you will usually be given a participant information sheet and time to read it. Good questions to ask the research team include:

• What is the trial trying to find out?
• What treatment will I get, and could I get a placebo?
• How many visits are involved, and how long will each take?
• What tests or procedures will I have, and are any extra to normal care?
• What are the possible risks and side effects?
• Can I keep taking my usual medicines?
• Will my travel or other costs be covered?
• What happens when the trial ends? Can I keep taking the treatment if it helps?
• Will I be told the results?

Take the information sheet home. Talk it over with family, friends or your own doctor. You should never be rushed into a decision.

Informed consent

Before you join, you will be asked to sign a consent form. Consent is more than a signature. It means you understand what the trial involves, the possible benefits and risks, and your rights.

Key points that apply in the UK, the US and the EU:

• Taking part is voluntary.
• You can withdraw at any time, without giving a reason, and your normal care will not be affected.
• You will be told about new information that might change your mind about staying in.
• Your personal data will be protected, and you will be told how it is used.

Every trial must be approved by an ethics committee, called a Research Ethics Committee in the UK and an Institutional Review Board in the US, as well as by the relevant regulator for trials of medicines. In the UK, the MHRA and the Health Research Authority now review medicine trials together through a single application, under regulations that came into force in April 2026. We report on how that is working in our article on six months of the new UK trial rules.

Costs and payments

In the UK, NHS trials do not charge participants. Many studies pay reasonable travel expenses, and some phase 1 trials in healthy volunteers pay for time and inconvenience. In the US, the trial sponsor usually pays for study-related care, but routine care may still go through your insurer, so ask what is covered before you agree.

What taking part is like

Trial participants are often seen more frequently than in routine care and have more tests. Some people value that extra attention. Others find the visits tiring. Ask for a realistic picture of the time involved.

Remember that a trial is testing whether a treatment works. You may benefit, you may not, and you may receive the comparison treatment. Many participants say they took part partly to help others with the same condition, and every trial, including ones that fail, adds to knowledge. Our guide to what it means when a trial fails explains why.

Spotting unreliable offers

Most trials are run responsibly, but you should be cautious about:

• clinics that charge you to receive an experimental treatment
• "trials" that are not on any public registry
• offers that promise a cure or guaranteed results
• pressure to decide quickly or to stop your usual treatment without your doctor's input

A genuine trial will have a registry number, ethics approval and a named research team you can contact.

After the trial

When a trial ends, ask for a summary of the results. In the EU, sponsors must post a plain-language summary on the public portal. In the UK, the Health Research Authority expects sponsors to share findings with participants. Expect a wait. Results can take a year or more to appear after the last participant finishes.

Our guide on how to read clinical trial results can help you understand what you are told.

A step-by-step summary for searching

1. Ask your specialist or GP whether there are trials for you.
2. Search Be Part of Research, ClinicalTrials.gov or the EU portal using your condition and location.
3. Check the phase, design and eligibility criteria.
4. Contact the study team or ask your doctor to refer you.
5. Read the information sheet, ask questions and take your time.
6. Decide, knowing you can leave at any time.

Finding the right trial can take some persistence. Each search becomes easier once you know the vocabulary and the questions that matter to you.

Related reading

• How new medicines get approved and reach patients
• Placebo and blinding in clinical trials explained
• What it means when a clinical trial fails