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 damaged 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 in the trial against damage or loss.

Individual NHS trusts are responsible for insuring themselves against damage caused by local studies. Research ethics committees would refuse approval for trials where there is no insurance or provision for compensation.

Before giving your consent to taking part in a clinical trial you may want to find out exactly what arrangements have been made for compensation. Your doctor or research nurse will be able to give you this information.