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The Basic Process of Clinical Trials

By Ella Cutter, Digital Marketing Manager, REPROCELL Europe
Clinical trials advance the future of medicine, benefitting both patients and practitioners.

New medicines, therapies and medical devices go through a rigorous journey before they reach the public domain. Currently, it takes 10-15 years on average to develop one new medicine from initial discovery through regulatory approval.1 At the heart of that process are clinical trials, which help researchers determine whether a new drug, device, or therapy is safe and effective for use in humans.

If you’ve ever wondered what really happens during a clinical trial, you’re not alone. Understanding the process can help you make an informed decision about participating in research and appreciate the vital role that medical research volunteers play in shaping the future of medicine.

Why Clinical Trials are Needed

Before a treatment ever reaches a clinical trial, it’s studied extensively in laboratories using cells, animal models, or human tissue.2 These early-stage studies can only go so far, providing valuable information on the best candidates to take forward. Eventually, scientists must test whether the treatment works for people, and that’s where clinical trials come in.

Clinical trials are essential for ensuring new treatments are safe to use in humans, measuring how effective they are at treating a condition, and identifying side effects and the best possible dose. Without clinical trials, we wouldn’t have vaccines, pain relief medications, cancer drugs, or many of the >20,000 approved therapies that people rely on today.3

The Phases of a Clinical Trial

Clinical trials are conducted in phases – each designed to answer specific questions about a new treatment.

Phase 0: These are small exploratory studies performed on small numbers of subjects (< 15 subjects) and using very small doses of the treatment to make sure the drug is not initially harmful in humans.

Phase 1: These trials are usually small (20-100 people) and usually involve healthy volunteers. These are sometimes called non-therapeutic trials. The goal is to assess safety, watch how the body processes the treatment, figure out the right dosage and identify any immediate side effects.

Phase 2: A slightly larger group of 100-300 people, who usually have the condition being treated but may include healthy people too. Here, researchers evaluate how well the treatment works, while continuing to monitor safety, as well as determining the ideal dose and delivery method (pill, injection, cream etc).

Phase 3: These larger studies include hundreds or even thousands of participants and compare the new treatment to the current standard therapies or placebos. Here, researchers look at how well the treatment works in a wider population and the data is used to apply for regulatory approval (FDA, MHRA).

 Phase 4: Once a treatment is approved and on the market, Phase 4 clinical trials continue to monitor its performance in the real world. It’s important to track long-term effectiveness of the new drug and any rare or delayed side effects, for years after its approved.4 

The Role of Medical Research Volunteers

No clinical trial can happen without research volunteers. Whether you’re living with a health condition or are perfectly healthy, your participation can help uncover life-changing treatments for others.5

Healthy volunteers are often needed to help researchers understand how the body normally responds, serve as a control group or test early-stage treatments for safety. Meanwhile, individuals with specific health conditions play a vital role in helping researchers understand how new treatments perform in real-world patients.

What Happens if You Take Part in a Clinical Trial?

If you’re interested in joining a clinical trial, here’s what you can generally expect:

Accessing a Clinical Trial

You can access or be recruited to clinical trials in various ways:
    • Directly through your clinical healthcare team if they are contributing to a trial - they may approach you if you fit the criteria
    • By responding to a clinical trial advert in your social feeds, radio and TV. You will be asked some questions to see if you are suitable to take part.
    • By proactively joining a research volunteer register. You will be asked to provide some basic details (e.g. health status, age, location) to help match you with relevant studies.

Reading the Information Sheet

Before you agree to take part, you’ll receive a detailed participant information sheet. This will cover the purpose of the study, what you’ll be asked to do, potential risks and your rights (like the ability to withdraw at any time).

Giving Informed Consent

If you’re happy to proceed, you’ll sign a consent form.
  • This is a formal agreement that shows you understand what’s involved. Participation is always voluntary, and you can leave the trial at any time.

Attending the Study Appointments

    • You may be asked to attend in person visits at a clinic, hospital or research site.
    • Some studies might involve one appointment, while others may span weeks, months or years.
    • You might provide a tissue specimen such as skin, blood, or urine, receive a new test treatment or placebo, complete surveys or diaries and return for follow up visits.

After the Study

    • Researchers may follow up with you to track long term outcomes or side effects.
    • You’ll often be told how the study went and what the next steps are.

Leaving the Study

    • You are always free to leave the study at any time, for any reason.
    • Patient safety and wellbeing are the top priority, and all trials are reviewed by independent ethics committees before they begin and are monitored throughout.7

Why Join a Medical Research Volunteer Registry?

Volunteer registries make it easier for researchers to find willing participants, especially for targeted studies like those involving specific skin conditions (e.g. psoriasis, eczema or inflammatory skin disease). By joining a registry, you help speed up the research process so that treatments can reach patients sooner. You will only be contacted about studies that match your interests and your availability, and participation is always your choice. Even if you don’t have a health condition, health volunteers play a key role, especially in early-stage safety trials or as control comparisons.

How do Research Volunteer Registries Work?

  1. Finding a Medical Research Volunteer Registry
  2. Joining a Research Volunteer Registry
    1. You sign up online to express interest in research.
    2. You’ll provide some basic details (e.g. health status, age, location) to help match you with relevant studies.
    3. You’re not committing to anything; it just means that you’re open to being contacted.
  3. Being Contacted About a Suitable Study
    1. If a researcher is running a study that fits your profile, they may contact you with details.
    2. This usually includes an overview of the trial, what’s involved, and how long it lasts.
  4. Participate in a Trial

Join our volunteer database and choose the studies that match your health profile, availability, and interests. Whether you’re healthy or living with a specific condition, you’ll be notified about research opportunities that are relevant to you—so you can decide if you’d like to take part.

Clinical trials are essential to advancing medicine, and they can’t happen without medical research volunteers. Whether you’re living with a condition or simply want to support future treatments, joining a medical research volunteer registry is a simple but powerful way to get involved. Your participation could improve or even save lives of many.

References: 

1. Derep, Maxime. “What’s the Average Time to Bring a Drug to Market in 2022?” N, N-SIDE, 11 May 2022, lifesciences.n-side.com/blog/what-is-the-average-time-to-bring-a-drug-to-market-in-2022.
2. Seladi-Schulman, Jill. “Clinical Trial Phases: What Happens in Phase 0, I, II, III, and IV.” Healthline, Healthline Media, 22 June 2019, www.healthline.com/health/clinical-trial-phases.
3. 2016, 28 January. “Without Clinical Trials We Would Have No New Drugs.” The Pharmaceutical Journal, 12 Feb. 2021, pharmaceutical-journal.com/article/news/without-clinical-trials-we-would-have-no-new-drugs.
4. Hunt. “Understanding the Phases of Clinical Trials: From Phase I to Phase IV.” Latest News Of Politics, Sports, World With Insquable, 15 Jan. 2025, insquable.com/understanding-the-phases-of-clinical-trials-from-phase-i-to-phase-iv/#:~:text=Clinical%20trial%20phases%20are%20structured%20steps%20in%20the,expanding%20the%20scope%20and%20scale%20of%20the%20research.
5. “Supporting Research without Taking Part in a Study.” Supporting Research without Taking Part in a Study - Be Part of Research, bepartofresearch.nihr.ac.uk/take-part-in-research/supporting-research-without-taking-part-in-a-study/. Accessed 12 Aug. 2025.
6. “What Will Happen to Me If I Agree to Take Part in a Clinical Trial?” NHS Choices, NHS, www.uclh.nhs.uk/our-services/find-service/cancer-services/cancer-clinical-trials/what-will-happen-me-if-i-agree-take-part-clinical-trial. Accessed 12 Aug. 2025.
7. “Clinical Trials .” NHS Choices, NHS, www.nhs.uk/tests-and-treatments/clinical-trials/. Accessed 12 Aug. 2025.
8. Zhang, H., & Jiang, X. (2025). Importance of clinical trials and contributions to contemporary medicine: commentary. Annals of medicine, 57(1), 2451190. https://doi.org/10.1080/07853890.2025.2451190

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