TRIALS
Phases that grow in size
The NHS says trials of new medicines go through a series of phases, from a small number of people to several thousand patients.
Step through the phasesHOW THE SYSTEM WORKS
Four phases,
then a licence.
No new medicine goes straight to the pharmacy shelf.
Step through the phases
PHASE 1 → 4safety, then scale
- Tested in phases
- Approved before it starts
- Licensed before it is sold
- The route from trial to prescription
It is tested in stages, first on a few people and then on thousands, checked by ethics committees and the regulator, and then judged on whether the NHS should provide it. This independent guide explains the route using NHS, MHRA, HRA and NICE pages. It names no medicines and gives no medical advice.
Updated
THE SHORT ANSWER
Tested, approved,
then appraised.
Three bodies look at a new medicine:
an ethics committee, the MHRA and, in England and Wales, NICE.
SAFEGUARDS
Approved before it begins
The MHRA must authorise a medicine trial, and all research involving people in the UK must first be approved by an independent research ethics committee.
Who checks what
ACCESS
A licence, then a decision
The MHRA must license a new medicine before it is marketed. In England and Wales, NICE decides whether the NHS should provide it.
See the numbersGeneral information only, not medical advice. For advice about your own health, speak to a doctor, pharmacist or other qualified health professional.
THE TRIAL PHASES
How many people
at each stage?
Pick a phase to see what the NHS says happens in it. The bar shows roughly how many people are involved, from a small group to wide everyday use.
From the NHS page on clinical trials. General information about how research works, not medical advice or a recommendation to join a trial.
TWO NUMBERS WORTH KNOWING
What NICE has
decided since 2000.
Figures from NICE's own appraisal data,
last updated 14 October 2026.
1,197
Technology appraisals since 1 March 2000
NICE has published 1,197 technology appraisals, giving 1,549 individual recommendations on medicines and other treatments.
APPRAISALS · NICE
87%
Recommendations that were positive
NICE says 87% of its recommendations have been positive: recommended, optimised (with some limits) or recommended for the Cancer Drugs Fund.
OUTCOMES · NICE
NICE says the NHS is legally obliged to fund and resource medicines and treatments recommended in its technology appraisals. Its figures exclude 177 appraisals where the company made no submission.
WHO CHECKS WHAT
Four checks
on the way.
The NHS, HRA, MHRA and NICE each describe a different part of the route. Here they are in order.
Ethics committee
The HRA says Research Ethics Committees protect the rights, safety, dignity and wellbeing of research participants.
MHRA trial authorisation
The MHRA reviews and authorises a trial of a new medicine before it begins, and inspects trial sites for good clinical practice.
MHRA licence
Trial results go to the MHRA, which decides whether the medicine can be marketed for a particular use. A licence shows it met standards of safety and effectiveness.
NICE appraisal
Independent NICE committees judge clinical and cost-effectiveness and make recommendations on NHS use in England and Wales.
INSIDE A TRIAL
Fair tests,
free to leave.
Most trials compare a new treatment with a control: a standard treatment or, where none exists, a placebo. A computer usually assigns people to groups at random, and many trials are 'blinded' so nobody knows who received which, to reduce bias.
The NHS says people can leave a trial at any point without giving a reason and without it affecting their care, and that researchers should make results available to participants. The Be Part of Research website lists UK studies.
Questions
Questions people ask
What is a clinical trial?
The NHS describes it as a study comparing the effects of one treatment with another. It may involve patients, healthy people, or both.
Who approves a trial of a new medicine?
The MHRA must review and authorise it, and all medical research involving people in the UK must first be approved by an independent research ethics committee, which the HRA manages in England.
What does a licence mean?
The NHS says licensing shows a treatment has met certain standards of safety and effectiveness. The MHRA must license a new medicine before it can be marketed.
Does a licence mean the NHS will provide it?
Not automatically. In England and Wales, NICE decides whether the NHS should provide treatments, and the NHS is legally obliged to fund treatments NICE recommends in its technology appraisals.
Why is safety still monitored after licensing?
Rare side effects that were not obvious in clinical trials may show up for the first time once many more people use a medicine, so the NHS says safety must be watched carefully in the first few years.