One in five people with cancer in the UK is involved in a research study, according to the latest National Cancer Patient Experience survey – the highest proportion in the world. Clinical trials are regulated investigations that often examine the effects of new treatments (drugs or devices), diagnostic tests or how care is given (eg, inpatient or day surgery). Without them there would be limited advances in medicine.

Trials are not just for the sick: all studies have to be done in phases, one of which includes healthy members of the public. Phase-one trials, which involve a drug being tested on a human for the first time, got bad press in 2006 when six men trying out the drug TGN1412 became seriously ill, with some of their organs failing. But early trials are usually safe, since drugs are first tested on animals and must get approval from the national licensing authority and an ethics committee. Participants can be paid and current ads offer anything from £200 to £2,000.

Phase-two trials take small numbers of people with a given condition (if it is for a new treatment) who are monitored closely. If the treatment seems to work the phase-three trial has many more patients, takes longer to find results and may be designed so that neither doctor nor patient knows who is having which treatment.

So why take part in a study? There is the lure of cash if you are a poor student, or of access to a new treatment if you have a serious disease and standard care has not worked. Patients with cancer often enter trials because they want to help other people with their disease. But are trials risky and do you need lots of tests?

The solution

You should talk to your doctor about whether you should take part in a trial. If you have cancer then Cancer Research UK has a database of trials on its website and a helpline (0808 800 4040). Other charities for specific conditions can access trial information and help you to decide.

Whether you are healthy or unwell, before signing up you should know exactly what the study is trying to discover: if it is looking at a treatment; what is known from earlier-phase trials; how it is likely to work. Find out how it will be given to you and the benefits and side effects that the researchers are expecting. You also need to know how much the trial will inconvenience you, how many extra tests you need, how unpleasant they might be and how often you will need to be checked at the hospital. Make a decision based on how much your quality of life will be affected. It is also useful to know who is funding the research, if the research team have a good history of getting their studies published and when the results will be reported.

If you are thinking of having the new treatment for a condition, you should investigate the quality of the treatment you will get if you do not try it. There is some research that suggests people enrolled in studies do better than those who do not.