Are clinical trials safe? Risks and benefits

The short answer

Clinical trials are carefully regulated, but no trial is risk-free.

Researchers are testing something that isn't fully understood yet, so there can be side effects nobody expected. The system of rules around trials exists to keep those risks as low as possible and to make sure you understand them before you join.

Who oversees trials

In the US, an Institutional Review Board (IRB) must approve every study that tests a drug or device or is federally funded — and most other studies — before it starts, and keep reviewing it while it runs.

An IRB is an independent committee that includes scientists and non-scientists, including at least one person from outside the institution. Drug and device studies are also overseen by the FDA, and many larger trials have a Data and Safety Monitoring Board — independent experts who look at results as the study goes and can pause or stop it.

How phases build safety step by step

New treatments move through phases, starting with small groups and widening only when earlier results look safe enough.

Phase 1 studies focus on safety and dose in a small number of people. Small does not mean low-risk: some Phase 1 studies, such as many cancer studies, test new treatments in patients and can carry real risks. Phase 2 and 3 studies include more people and keep tracking side effects. Each step adds information before more people are asked to take part.

Common risks

Possible risks include side effects from the treatment, discomfort from tests like blood draws or scans, and the chance that the treatment doesn't work for you.

There are also practical costs: time, travel and extra appointments. The consent form lists the risks the researchers know about, and the team must tell you about important new ones as they learn them.

How your safety is monitored

During a trial, the team checks on you regularly through visits, tests and questions about how you feel.

You will have a contact to call if something changes. Serious, unexpected problems must be reported to the IRB and, for many studies, the FDA. If a treatment looks harmful, the study can be changed or stopped.

Possible benefits

Possible benefits include access to a new treatment before it is widely available (which may or may not help you), close medical attention, and helping future patients.

A benefit is never promised. Some participants receive a placebo or the current standard treatment, and a new treatment may turn out to work no better than existing ones.

Weighing it up

Talk through the risks and benefits with the study team and your own doctor before deciding. You can ask what is known so far, what side effects earlier participants had, and what happens if you get sick during the study. Ask what happens and who pays if you're injured because of the research — the consent form must explain this. Joining is always your choice, and you can leave at any time.

Browse related trials

• Breast Cancer trials
• Alzheimer's Disease trials
• Heart Failure trials

Quick answers

Are clinical trials safe?

Clinical trials are carefully regulated, but no trial is risk-free.

Who makes sure a clinical trial is safe?

In the US, an Institutional Review Board (IRB) must approve every study that tests a drug or device or is federally funded — and most other studies — before it starts, and keep reviewing it while it runs.

What are the common risks of a clinical trial?

Possible risks include side effects from the treatment, discomfort from tests like blood draws or scans, and the chance that the treatment doesn't work for you.

How is my safety monitored during a trial?

During a trial, the team checks on you regularly through visits, tests and questions about how you feel.

What are the benefits of joining a clinical trial?

Possible benefits include access to a new treatment before it is widely available (which may or may not help you), close medical attention, and helping future patients.

Sources

• 21 CFR Part 56 — Institutional Review Boards
• 45 CFR Part 46 — Protection of Human Subjects (Common Rule)
• FDA — Step 3: Clinical Research (phases and typical length)
• NIH — Clinical Research Trials and You: The Basics