Healthy Subjects

Not every clinical study is for people living with a medical condition. Many need volunteers who are well, because the question is what happens in a body that is not already dealing with the illness under study. If you have no diagnosis and have wondered whether you can take part in research, this is the page for it. Read it alongside why join a study.

What healthy-volunteer research is

A healthy-volunteer study enrols people who are not being treated for the condition the research is about. The purpose is not to treat you. It is to measure something clearly: how quickly the body absorbs and clears an investigational medicine, how the immune system responds to a vaccine, or what a normal result looks like on a new test. Those measurements shape the studies that follow in people who are unwell.

The kinds of studies that need volunteers who are well include:

• Phase 1 studies, usually the first time an investigational medicine is given to people, measuring what the body does to the medicine and what the medicine does to the body
• Vaccine studies, which measure the immune response and record side effects across several visits
• Bioequivalence studies, which compare how two versions of an approved medicine behave in the body
• Device, imaging and diagnostic studies, which need results from people without the condition
• Control groups in larger studies, comparing results from people who are well with results from people living with a condition
• Observational studies and sample collection, which involve no treatment at all

What taking part involves

Every study is different, and the written information you receive sets out what yours asks of you. It starts with screening: a health questionnaire, a physical examination, blood and urine tests, often an electrocardiogram, and a pregnancy test where that applies. Screening confirms you meet the study’s own definition of healthy, and it can pick up things you did not know about. Those results are yours, and anything unexpected is discussed with you.

The commitment might be a single morning, several visits over weeks, or a stay at a research unit where samples are taken at set times over a day or more. You may be asked to avoid certain foods, alcohol or medicines beforehand, to fast before blood tests, or to keep a diary. There are usually restrictions on donating blood or joining another study afterwards. All of this is explained before you decide, and the consent conversation is the point at which to ask how much of your time it will take.

Who is usually not eligible, and why

• People living with an unstable or untreated medical condition, because it affects both the results and their safety.
• People taking regular prescription medicines, and sometimes over-the-counter medicines or supplements, since these change how an investigational medicine behaves.
• People who are pregnant or breastfeeding are excluded from most healthy-volunteer studies.
• People outside the study’s age range. Ranges are deliberate, and some studies specifically want older adults.
• People who recently took part in another study or donated blood, where a waiting period applies.
• People who cannot attend all the visits, because missed visits make the data unusable.

None of these are judgements about you. They are how a study keeps its results interpretable and its participants safe, and a study that is not a fit today may be a fit later.

Why research in this area matters

Almost every medicine and vaccine in routine use passed through healthy volunteers first. Without that step there is no basis for deciding how much to give, how often, or what to watch for once people who are unwell start receiving it. Healthy volunteers also make comparison possible: many studies cannot interpret results from people living with a condition without results from people who do not have it. Canada does a substantial share of this work, with roughly 3,100 trials under way in 2025.

The terms are the same as in any other study. Participation is voluntary, and every study is reviewed by a research ethics board before it starts. You receive plain-language written information and give informed consent before anything is done, and consent is a conversation rather than a signature. You can withdraw at any time, without giving a reason, and it will not affect the care you get from your own doctor. No one can tell you in advance how a study will affect you personally, and taking part is not a health check or a substitute for one.

Learn more from Canadian sources

• Canada’s search portal for clinical trials
• Health Canada: Clinical Trials Database
• Tri-Council Policy Statement on ethical conduct for research involving humans
• Invest in Canada: clinical trials in Canada