Guide
What to know before joining a clinical study
Clinical studies test new medicines, devices and approaches to care. Taking part can give you access to new treatments and closer monitoring, but it also takes time and carries risks. This guide covers what to expect and what to ask.
What a clinical study is
A clinical study (also called a clinical trial or research study) is a carefully planned project that answers a specific health question, such as whether a new medicine works better than an existing one. Studies follow a written plan called a protocol, and in the United States most are overseen by an independent review board that checks they are ethical and that participants are protected.
Some studies test a treatment. Others only observe people over time, collect samples, or ask about experiences. Many studies also need healthy volunteers.
Study phases
| Phase | Main question | Typical size |
|---|---|---|
| Phase 1 | Is it safe, and what dose works? | Tens of people, often healthy volunteers |
| Phase 2 | Does it seem to work, and what side effects show up? | Up to a few hundred people with the condition |
| Phase 3 | Does it work better than, or as well as, current treatment? | Hundreds to thousands of people |
| Phase 4 | How does it perform after approval, in everyday use? | Can be very large |
Who can join
Every study lists eligibility criteria: who can take part (inclusion criteria) and who can't (exclusion criteria). Common criteria include age, diagnosis, current medicines, other health conditions, and recent test results. The criteria protect participants and make the results reliable.
Matching a description you read online doesn't mean you are eligible. The study team checks eligibility through a screening process, which can include questions, a medical history review and tests.
Compensation and costs
Some studies pay participants for their time and travel. Amounts vary widely by study, and many studies offer no payment. The study's consent form should explain:
- Whether you'll be paid, how much, and when.
- Which costs the study covers, such as study visits, tests and the study treatment.
- Which costs might still fall to you or your insurance.
Payment shouldn't be the main reason to join a study. Be wary of any listing that promises large or guaranteed payments.
Possible benefits and risks
Possible benefits: access to a new treatment before it is widely available, close monitoring by a research team, and helping research that may help others with the same condition.
Possible risks: side effects that aren't yet known, a treatment that turns out not to work for you, receiving a placebo (an inactive treatment) in some studies, and the time needed for visits and tests.
You can leave a study at any time, for any reason. Leaving shouldn't affect the regular care you receive.
Questions to ask before you agree
- What is the study trying to find out?
- What will I be asked to do, and how many visits are there?
- Could I receive a placebo?
- What are the known risks and side effects?
- Will I be paid or reimbursed for travel? What costs might I have to cover?
- Who will see my health information, and how is it protected?
- What happens at the end of the study? Can I keep taking the treatment if it helps?
- Who do I contact if I have a problem or want to leave?
Bring this list to your screening visit, and talk it through with your own doctor too.
Finding a study
The official U.S. registry of studies is ClinicalTrials.gov, run by the National Library of Medicine. Our study search uses its listings to show studies recruiting near your ZIP code. It asks a few quick questions and never asks for your name, email or phone.
Sources: ClinicalTrials.gov: Learn About Studies; NIH: Clinical Research Trials and You. This guide is general information, not medical advice.