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Clinical Trial | Overview

How do clinical trials work?

For most clinical trials a participant is assigned to either an intervention or a control group. Intervention group participants receive the intervention that is being tested. Control group participants do not receive the intervention. Instead they might receive the standard treatment for the disease or condition, or they might receive a placebo, which looks or feels like the intervention, but it is not an active medicine or treatment. The control group helps the researchers understand the effects of the experimental intervention.

Your group assignment often happens by chance. If you take part in a clinical trial, you might not get the experimental treatment that is being tested. In some cases, you won’t know the group to which you are assigned.

Potential benefits and risks of clinical trials

There are benefits and risks for research participants. Being part of a clinical trial allows the participants to have access to experimental treatments that are not yet available to the public, while also helping others by contributing to the development of a new medical treatment or procedure. Additional benefits include:

  • helping others by contributing to knowledge about new treatments or procedures
  • gaining access to new research treatments before they are widely available
  • receiving regular and careful medical attention for a research team that includes doctors and other health care professionals

Risks for research participants include:

  • receiving an experimental treatment when its effects are not yet fully understood
  • unpleasant or even serious side effects from some tests and procedures
  • minor discomfort
  • complications that require medical attention

The specific risks associated with a research protocol are described in detail in the informed consent document, which participants are asked to consider and sign before participating in research. Also, a member of the research team will explain the study and answer any questions about the study. Before deciding to participate, it's important to carefully consider risks and possible benefits.

Where do I find clinical trials?

One good way to find out if there are any clinical trials that might help you is to ask your doctor. Other sources of information include:

  • FDA Clinical Trials Search. Search a database of Federally and privately supported studies available through Learn about each trial’s purpose, who can participate, locations, and who to contact for more information.
  • Conduct more advanced searches
  • National Cancer Institute or call 800-4-CANCER (800–422–6237). Learn about clinical trials for people with cancer.

Are clinical trials safe?

The FDA works to protect participants in clinical trials and to ensure that people have reliable information before deciding whether to join a clinical trial. The Federal government has regulations and guidelines for clinical research to protect participants from unreasonable risks. Although efforts are made to control the risks to participants, some may be unavoidable because we are still learning more about the medical treatments in the study.

The government requires researchers to give prospective participants complete and accurate information about what will happen during the trial. Before joining a particular study, you will be given an informed consent document that describes your rights as a participant, as well as details about the study, including potential risks. Signing it indicates that you understand that the trial is research and that you may leave at any time. The informed consent is part of the process that makes sure you understand the known risks associated with the study.

You and your doctor are a team in your care. This material is for informational purposes only and it is not intended to be a substitute for medical advice. Talk to your doctor to decide the right course of treatment for you.