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What is a clinical study?
Clinical studies are how medicine learns what works, for whom, and how safely.
Last reviewed 14 September 2026
In short
A clinical study is research that involves people. It answers a specific question about health, such as whether a new treatment works better than the usual one, or how a condition changes over time.
Every study follows a written plan, called a protocol, that sets out who can take part, what happens, and how the results are measured.
Two main kinds
Interventional studies (clinical trials)
Participants receive something specific, such as a medicine, device, procedure or behaviour change, so researchers can measure its effects.
Observational studies
Researchers watch and measure without assigning a treatment, for example following how a condition develops.
Why people take part
To get access to a treatment that isn't widely available yet.
To help researchers understand a condition they or someone they love lives with.
To contribute to care that helps other people in the future. Healthy volunteers are needed too.
This is general information, not medical advice. Talk to your doctor about whether a study could be right for you, and to the study team about the details of a specific study.
Sources
Written from public information published by ClinicalTrials.gov (U.S. National Library of Medicine) and the U.S. National Institutes of Health.