What happens during and after a clinical trial?

If you’re thinking of taking part in a clinical trial, or have been invited on to one by your doctor, then you will be wondering how the process works in practice.

Here’s a guide to what might happen – before, during and after your trial.

Before your clinical trial

Giving your informed consent

Before you take part in a trial, a doctor or other researcher should make sure you have given your informed consent. Before you can do this, you will need to understand the purpose of the trial and how it affects you, including the main risks and benefits of taking part.

For more information on the questions to ask, see our section on what you should know before choosing to join a trial.

 You'll need to know how the trial might affect you before you can give your consent

Being allocated to treatment groups

Control groups

In some clinical trials, known as controlled trials, participants are divided into groups before the trial begins.

If you are in what is known as the trial group or intervention group, you may be given the new treatment that is being tested. But if you are allocated to what is known as the control group, you may be given an existing treatment, no treatment, or a placebo (a treatment that looks like the new one, but does nothing). Which one you get depends on how the trial is designed.

The idea of this ‘control’ group is to have a group of people to compare the intervention group against – so researchers can work out whether any improvement is due to the new treatment.

If you are in the control group, you are still a very important part of the trial: the results from this group are what the effects of the test treatment are compared with. Also, don't forget, the treatment being tested may be no better than the control, which is why the trial needs to be done.

Blind and double-blind trials

In a ‘blind’ trial, researchers won’t tell you which group you’re in – which means you might be receiving either the new treatment or the control, but you won’t know which. (To prevent you from guessing which treatment you’re getting, the treatments are made to look as similar as possible.)

Researchers design blind trials because if you knew which treatment you were getting, it could influence how you feel, or how you report your symptoms.

Some trials are ‘double-blind’, which means that neither you nor the doctors treating you know who is getting which treatment, until the team leading the trial “break the code” to reveal this.

'Randomised' trials

In ‘randomised’ trials, you will be allocated to treatment groups at random, usually with the help of a computer program. This is done to minimise doctor or patient influence on the trial results.

During your trial

Once you are on a clinical trial, the researchers running the trial will want to carry out regular tests on you to find out how your treatment is working.

At the same time, they will be on the lookout for any side effects – so you may be asked questions about any new symptoms you have, including psychological symptoms.

You may also be asked to fill out questionnaires or to keep a diary. Sometimes this means going to your hospital or GP more often than you would normally, so bear this in mind before you agree to take part.

Researchers will also look at the wider effects of a treatment on your life as a whole – in other words, your ‘quality of life’. So they may ask you if you’re able to take part in your usual day-to-day activities, or if you need any extra help around the home or to look after your family.

Some clinical trials will look at the cost-effectiveness of treatments or their effects on other aspects of your life. So you might be asked whether you’re able to work, or the number of times you visit your doctor or nurse.

The benefit to you of this extra attention is that any changes in your health, whether or not they are related to the treatment you are having, are frequently picked up and acted upon earlier than if you were not in a trial.

However, some people find that the extra attention makes them worry more about their condition and prevents them from ‘getting on with their life’.

After your trial

How will trial results be used?

At the end of a trial, the results should be made available to everyone who took part if they want them. They should also be published, so that others can use the information to help them make decisions about treatment and healthcare.

Researchers should publish the results, regardless of what they show, and also demonstrate how the results add to available knowledge.

The government and charities usually publish the findings of trials they have funded and some drug companies are also now committed to openly registering trials and making their results public. The Department of Health/National Institute for Health Research insists on publication of the results of all research studies that it funds.

At NIHR, we publish the results of all our medical research here. Because some trials can run for many years, it may be some time before the results of a trial are known.

Continuing your treatment

If you are having a new treatment as part of a trial, you might naturally want to continue that treatment after the trial ends. But in practice, it may not always be possible for you to do this.

It may also be some time before a new treatment is provided by the NHS. In this case, you will be given the standard treatment for the condition you have.

In some circumstances you may be able to buy the new treatment on a private basis; for example, if the drug has a licence, but is not available on the NHS.

How is it decided whether to make a treatment available?

Patients sometimes ask why a drug or device that seems to work in a trial is not always made available on the NHS once it ends.

An independent public body, the National Institute for Health and Care Excellence (NICE), recommends whether the NHS should buy new and existing treatments. 

It makes these decisions based not only on how well a treatment works, but also on whether it represents value for money. Sometimes, treatment costs only become entirely clear after a trial. For example, the high cost of a new drug might be compensated for if it reduces the need for outpatient visits. However, until a trial is complete and analysed, such things are unknown. This is why it is impossible to be certain, when a trial starts, about whether or not the test drug or device will be made available on the NHS following the drug trial or research study.

All NICE recommendations are subject to regular review, and any new trials that take place after it makes a recommendation are taken into account. NICE also goes on gathering data about how drugs are used in practice, to feed into future decisions.

Patients can get involved with NICE's work. Find out more here