Joining a clinical trial 

If you take part in a clinical trial, you may be one of the first people to benefit from a new treatment. However, it may turn out to be no better, or to be worse, than the standard treatment.

This page explains:

Many people choose to take part in clinical trials because it helps increase understanding of how to treat a particular disease or condition. This may benefit them, or others like them, in the future.

Finding out about clinical trials 

If you're ill and interested in taking part in a clinical trial, your doctor or other healthcare professionals may know of research being carried out that may be right for you. However, few healthcare professionals know of all the trials being carried out in their clinical area. There could be dozens, or even hundreds.

Searching the registers

You can look for information on the registers of clinical trials, such as the World Health Organization's International Clinical Trials Registry Platform (ICTRP). This collects information from different registers to provide a central database of clinical trials.

Many of the topics in the Health A-Z have a page that allows you to search for WHO-registered clinical trials for that particular condition or treatment. You can also search for clinical trials from these topics.

None of the registers covers all the trials currently being carried out in the UK. However, the UK Clinical Trials Gateway provides information about clinical trials in the UK from several different registers.  

You'll probably need to talk to your doctor or specialist nurse about any information on trials you've found in the registers.  


For some conditions, you can find out about trials from patient organisations. For example, Cancer Research UK has clear information on nearly all the cancer clinical trials happening in the UK.

Other health charities also have user-friendly information about some clinical trials. Charities that aren't listed may not formally publish lists of clinical trials, but may know of some that are relevant to patients with particular conditions.

User-friendly clinical trials information includes:

Questions to ask

When you express interest in a trial, a doctor or nurse is likely to tell you something about it in person. You'll also be given some printed information to take away. You may come back with some questions you feel haven't been answered.

The UK Clinical Research Collaboration is a partnership of organisations that are establishing the UK as a world leader in clinical research. It suggests a number of general and practical questions you may want to ask.

General questions

  • What is the aim of the trial and how will it help people?
  • Has existing evidence been reviewed systematically?
  • Who is funding the trial?
  • What treatment will I get if I do not take part in the trial?
  • How long is the trial expected to last, and how long will I have to take part?
  • How long will it be before the results of the trial are known?
  • Is there an explicit commitment to report the results of the trial? 
  • What will happen if I stop the trial treatment or leave the trial before it ends?

Practical questions

  • How much of my time will be needed?
  • What extra tests or appointments will I have?
  • Will I need to take time off work?
  • Will I need extra help from family or friends?
  • Will the costs of my travel to take part in the trial be covered?
  • If the trial is testing a new drug, will I have to collect it from the hospital, will it be sent to me by post, or will I get it through my doctor?
  • Will I have to complete questionnaires or keep a diary?
  • What are the possible side effects of my treatment?
  • How could the treatments affect me physically and emotionally?
  • Who can I contact if I have a problem?
  • Will someone be available 24 hours a day?
  • How do I find out the results of the trial?

Advantages of being in a clinical trial

The main reason for carrying out trials is to assess whether one treatment is better than another.

During the trial, your treatment and progress may be monitored more closely than if you were receiving the usual treatment.

After the trial has finished, healthcare professionals will be better able to offer you the most appropriate and effective treatment for you.

Trials are very important in helping find better treatments. By being involved in a trial, you'll obtain information and evidence that may be helpful to you in the future, as well as helping the NHS provide people with the best possible standard of care.  

Disadvantages of being in a clinical trial

The disadvantages of being in a trial are:

  • As with any treatment, you can't be sure of the outcome. 
  • You may be given a new treatment that turns out not to be as effective as the standard treatment.
  • It's possible you'll experience unexpected side effects.
  • You may have to visit your place of treatment more often, or have more tests, treatments or monitoring than you would if you were receiving the standard treatment in usual care. 

Giving consent

If you're asked to take part in a trial, you're free to say yes or no. For people under the age of 18, a parent or guardian has to give permission. The doctor organising your treatment will usually talk to you about being involved. They should explain the possible risks and benefits.

Make sure you're happy with the trial and have been given all the information you want before you give your consent (permission). This may mean taking some time to think about it and talk it over with family or friends, unless a decision is needed urgently because of your medical condition.

If you decide to take part, you'll be asked to sign a form to say you're agreeing to take part in a trial and have understood what it involves. This is called giving your informed consent.

Why you might not be able to take part

Sometimes it may not possible for you to be involved in a particular trial. For example:

  • Your condition may need to be at a particular stage.
  • You may not be allowed to receive another treatment at the same time. 
  • Some trials seek people with certain illnesses and conditions, while others need healthy people. 
  • Some trials need people of a certain age.
  • There may already be enough people in a particular category who have joined the trial.

Medical tests

Before you join a trial, you may need to have tests to see if you can take part. For example, you may have to be tested to see if you have raised levels of a particular hormone.

This will give the researchers more information about your health before you start treatment, which will allow them to tell whether there's been an improvement at the end of the trial.

During the trial, you may have more tests to see whether the treatment is working. It may be possible for the tests to be carried out as part of your routine care, or you may have to make more visits than usual to your GP or hospital clinic.

Leaving a trial

You may decide to stop taking part in a trial if your condition is getting worse or if you feel the treatment isn't helping you. You can also choose to leave at any point without giving a reason and without it affecting the care you receive.

If there are signs that the treatment in a trial could be unsafe, the research team or the regulators will stop the trial. Read more about how trials are regulated.

Video: NHS Health Research

Find out about primary care research in the NHS, and see how you can get involved

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Next review due:

Page last reviewed: 05/01/2015

Next review due: 05/01/2017