Safety in clinical trials

If you decide to take part in a clinical trial, you are protected in lots of ways.

  • The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) makes sure clinical trials meet high standards of practice and that all serious side effects are reported.
  • All clinical trials have to be approved by a research ethics committee. These are independent groups made up of a mixture of health professionals and non-medical people. They ensure patients are given all the information they need.
  • Data monitoring committees monitor the safety of a clinical trial and how well a treatment is working. They can stop a trial if it is causing harm to a person.
  • All clinical trials have some form of insurance to compensate patients in the unlikely event something goes wrong.

How safe are clinical trials?

Understandably, anyone who enters a clinical trial will want to know that it’s safe for them to do so. There are a number of ways people are protected both before and during a trial.

Medicines and Healthcare products Regulatory Agency (MHRA)

The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) makes sure trials meet international standards of good practice, which are there to protect people taking part. All serious side effects must be reported.

Research Ethics Committees

All research in the UK involving people, whether done in the NHS or private sector, has to be approved by an ethics committee. These are independent groups that put the rights, safety, dignity and well-being of research participants at the centre of their decision making. They make sure that patients are fully informed, and that they will be compensated if anything goes wrong. The committees are often based at local hospitals and must be made up of a mixture of health professionals and other non-medical people. They often include patients, lawyers and members of the public.

Monitoring trials and stopping rules

Before a trial begins, a data monitoring committee is usually set up to monitor patient safety and the effectiveness of the treatment during the trial.

The data monitoring committee can stop a trial if they are concerned that a new drug or treatment is causing harm to a person. For example, they can stop a trial if there are severe side effects. This is unlikely to happen in phase 3 or 4 trials because the new drug or treatment has already been extensively tested during phases 1 and 2.

Trials can also be stopped early if the results of the new treatment are much better than the standard treatment. The new treatment can then be used instead of the standard treatment so that everyone in the trial can benefit from it.


The drugs used in clinical trials are made to the highest standards of purity and quality. Drug companies are insured so that if a patient is harmed by some unforeseen event due to the drug, compensation can be paid. It’s rare for patients to be harmed by trial drugs although some may cause unpleasant side effects.

Trials funded by the Department of Health, the UK Medical Research Council or medical charities may not have this kind of insurance, but a payment would be made if something did go wrong.

All trials will have a legal sponsor. One of the sponsor’s roles is to make sure that there are arrangements, such as insurance, to protect those taking part against damage or loss. Individual NHS trusts are responsible for insuring themselves against harm caused by local trials. Research ethics committees would refuse approval for trials where there is no insurance or provision for compensation.

Back to Can and should I take part?

Questions to ask

You may like to ask your doctor or nurse some questions before deciding whether to take part in a clinical trial.

Taking part in a trial

Clinical trials are confidential and you won’t be entered into one without giving your consent.