The Complete Guide to Clinical Trials in the UK

1. What Are Clinical Trials?

A clinical trial is a research study involving human volunteers that tests new medical treatments, drugs, devices, or new ways of using existing treatments. Every medicine your doctor prescribes today — from paracetamol to cutting-edge cancer immunotherapy — was once tested in a clinical trial.

Clinical trials are the gold standard for determining whether a new treatment is safe and effective. They are carefully designed, reviewed by independent ethics committees, and approved by regulatory authorities before any participants are enrolled.

Clinical trials have given us every major medical breakthrough of the last century — from antibiotics and vaccines to HIV treatments and cancer immunotherapy.

Types of clinical trials

• Treatment trials — test new treatments (drugs, surgery, radiation therapy, devices)
• Prevention trials — test ways to prevent disease (vaccines, lifestyle changes, supplements)
• Screening trials — test new ways to detect disease early
• Diagnostic trials — compare tests or procedures for diagnosing conditions
• Quality of life trials — explore ways to improve comfort and daily living for people with chronic illness

2. The Four Phases of Clinical Trials

Before a new treatment reaches patients, it goes through a series of progressively larger studies. Each phase has a specific purpose.

3. Why Clinical Trials Matter

Clinical trials are the engine of medical progress. Without them, new treatments would never reach patients. Here's why they matter:

• They prove treatments work — a treatment isn't approved until clinical trials demonstrate it is safe and effective
• They protect patients — every trial follows strict safety protocols and is monitored by independent ethics committees
• They advance medicine — trials have led to cures for previously untreatable conditions (e.g., Hepatitis C, certain childhood leukaemias)
• They give patients options — for many conditions, a clinical trial offers access to the newest treatments years before they become widely available

4. Who Can Participate?

Clinical trials need a wide range of participants. The idea that trials are only for seriously ill patients with no other options is outdated. Today, trials need:

• Healthy volunteers — for Phase 1 and bioequivalence studies (often compensated £500–£3,000+)
• Patients with specific conditions — from common conditions like asthma and diabetes to rare diseases
• People of all ages — including children (with parental consent) and older adults
• People from diverse backgrounds — because treatments can affect different populations differently

Eligibility criteria

Every trial has specific inclusion and exclusion criteria. These define who can and cannot participate, based on factors like:

• Age range
• Type and stage of condition
• Previous treatments
• Other health conditions (comorbidities)
• Biomarker or genetic profile (e.g., BRCA+, EGFR mutation, HER2+)
• Current medications

These criteria exist to protect participants and ensure the trial produces meaningful results. If you don't match the criteria for one trial, you may still be eligible for another.

5. How to Join a Clinical Trial

Joining a clinical trial is a straightforward process. Here's what to expect:

6. Safety, Ethics & Your Rights

Patient safety is the top priority in clinical trials. Multiple layers of protection exist:

Regulatory oversight

• MHRA (Medicines and Healthcare products Regulatory Agency) — authorises all clinical trials of medicines in the UK
• NHS Research Ethics Committees — independent committees that review the ethics of every trial
• Health Research Authority (HRA) — provides overall governance of health research in England
• Data protection — your personal data is protected under UK GDPR and the Data Protection Act 2018

Your rights as a participant

• You can withdraw at any time, without giving a reason, without affecting your NHS care
• You receive full information about the trial before you agree to participate
• Your data is anonymised and stored securely
• You have the right to know the results of the trial when it finishes
• You are monitored closely for any side effects throughout the trial
• Serious adverse events are reported immediately to the regulatory authorities

7. Clinical Trials in the NHS

The NHS is one of the largest clinical trial hosts in the world. The National Institute for Health and Care Research (NIHR) supports and delivers research across NHS hospitals, GP practices, and community settings throughout England.

How NHS trials work

• Your NHS consultant or GP may invite you to join a relevant trial as part of your care
• You can also find NHS-hosted trials on TrialConnect by searching your condition
• NHS trials follow the same strict ethical and safety standards as industry-funded trials
• Being in a trial does not affect your right to standard NHS care
• Your trial team and your NHS care team work together to coordinate your treatment

NHS research infrastructure

The NIHR Clinical Research Network (CRN) coordinates research across 15 local areas in England. Key facts:

• Over 1 million participants take part in NIHR-supported research each year
• Research is conducted across all NHS settings — hospitals, mental health trusts, GP practices, and community services
• The UK government has set a goal for all patients to have the opportunity to take part in research by 2027

8. Paid Research Studies for Healthy Volunteers

If you're a healthy adult, you can earn money by participating in clinical trials. Pharmaceutical companies need healthy volunteers to test new medicines before they are given to patients.

What's it like?

• You stay in a comfortable clinical research unit with private rooms, meals, WiFi, and entertainment
• Medical staff monitor you around the clock
• You give regular blood samples and may have vital signs checked
• Most units have lounges, TVs, and games consoles
• You undergo thorough health screening before being accepted
• You can leave at any time, though your compensation may be reduced

Read more in our guide: How Paid Clinical Trials Work

9. Modern Treatments: Biomarkers, Immunotherapy & Gene Therapy

Clinical trials are evolving rapidly. Modern trials increasingly use precision approaches to match the right treatment to the right patient.

Biomarkers and precision medicine

A biomarker is a measurable indicator of a biological state — like a gene mutation (BRCA1, EGFR), protein level (PSA, CA-125), or blood test result (HbA1c). Many modern trials use biomarkers to identify which patients are most likely to benefit from a particular treatment. This approach is called precision medicine or personalised medicine.

TrialConnect's Smart Matcher lets you specify your biomarkers to find trials that match your genetic profile.

Immunotherapy

Immunotherapy harnesses your immune system to fight disease. It has transformed cancer treatment, particularly for melanoma, lung cancer, and lymphoma. Common immunotherapy approaches include:

• Checkpoint inhibitors (e.g., pembrolizumab, nivolumab) — "release the brakes" on immune cells
• Monoclonal antibodies — target specific proteins on cancer cells
• CAR-T cell therapy — your own immune cells are genetically modified to attack cancer
• Cancer vaccines — train the immune system to recognise cancer cells

Gene therapy

Gene therapy modifies or replaces genes to treat or prevent disease. Breakthrough gene therapies have been approved for sickle cell disease, haemophilia, and certain eye conditions. CRISPR gene editing technology is being tested in clinical trials for multiple conditions.

10. Finding the Right Trial for You

TrialConnect makes it easy to find clinical trials that match your specific situation. Here's how:

Useful resources

• NHS — Clinical Trials
• NIHR — How to Get Involved in Research
• Health Research Authority
• MHRA — Clinical Trial Approval
• ClinicalTrials.gov — trial data source

Related guides