There may be a delay before the results of a clinical trial are known, particularly with larger trials that can involve thousands of people and may take place over several years.
Even when the results have been collected and analysed, there is a further period, usually several months, when the research is looked at and commented on by other scientists as a check on its quality. This is called peer review.
At the end of the trial, the researchers should make the results available to anyone who took part and who said they want to know the results.
If the researchers do not offer you the results and you want to know, ask for them.
All the main public funders of health research and the larger medical research charities require researchers to place a copy of their research on UK PubMed Central when it is published. This is a condition of funding.
Licensing a treatment
If research has identified a new medicine, the Medicines and Healthcare products Regulatory Agency (MHRA) must license it before it can be marketed.
Licensing shows that a treatment has met certain standards of safety and effectiveness.
Safety must be monitored carefully over the first few years of a newly licensed treatment because rare side effects that were not obvious in clinical trials may show up for the first time.
In England and Wales, the National Institute for Health and Clinical Excellence (NICE) decides whether the NHS should provide the new treatment.
