Clinical trials are an important part of developing new treatments. Before any new drug or therapy is available to the public, it must go through a careful testing process. These steps, called the phases of clinical trials, help make sure the treatment is safe and that it works.

Each phase builds on the one before it. Here's what you need to know.

Phase 1: Is It Safe?

The first phase of a clinical trial is all about safety. This phase usually involves a small group of people—often healthy volunteers. The goal is to see how the body reacts to the new treatment.

Researchers start with a low dose and slowly increase it. They watch closely for any side effects or reactions. This helps them figure out the right dose to use in future phases.

Phase 2: Does It Work?

If the treatment is safe in Phase 1, it moves on to Phase 2. This time, the focus is on whether the treatment actually works for the condition it's meant to help.

This phase includes more people—often several hundred. Some people receive the treatment, while others may get a placebo or a standard treatment for comparison. Researchers look at how well the treatment works and continue tracking side effects.

Phase 3: Is It Better?

Phase 3 is a bigger test. It usually includes thousands of people. Researchers want to know: Is this new treatment better than what's already out there?

They look at how well it works, what side effects appear over time, and how it affects daily life. The results from this phase are used to decide whether the treatment should be approved for public use.

Phase 4: What Happens Over Time?

Even after a treatment is approved, the work isn’t done. In Phase 4, also called post-marketing studies, researchers continue to study the treatment in the real world.

They look at long-term safety and any new side effects. They also learn how the treatment works in different groups of people and when used with other medications. Sometimes, new information from this phase leads to updates in how the treatment is used—or in rare cases, it may be taken off the market.

You Are Part of the Process

Clinical trials can’t happen without people like you. When you join a trial, you’re helping researchers find better treatments—and helping others who live with your condition. You’re not just a participant; you’re part of the care team.

If you’re interested in clinical trials, talk to your doctor and explore trusted resources. And if you’re a member of Inspire, you can read stories from others in your community who’ve participated in trials.

From the Inspire Community

Want to know what it’s really like to take part in a trial? Check your community on Inspire to read posts from people who’ve been there. Their stories can offer hope, tips, and real-world advice from people who understand.

Disclaimer

Member comments are lightly edited for length and to remove identifying information but are otherwise reproduced as they appear in the community as part of public posts. This content is for general informational purposes only and does not necessarily reflect the views and opinions of any organization or individual. The content should not be used as a substitute for professional medical advice, diagnosis, or treatment. Please consult your healthcare provider about any questions you may have regarding a medical condition.

Sources:

• Clinical Research: Benefits, Risks, and Safety. National Institute of Aging. May 2023.

• Phases of Clinical Trials. American Cancer Society. June 2025.

• Placebo in Clinical Trials. National Library of Medicine.

• Side Effects in Clinical Trials. Medical Life Sciences News.

• Post-marketing Studies. United States Food & Drug Administration (FDA).