Informed consent is how researchers give information about a clinical study to people who are already part of a study (participants) as well as to those who are thinking of being part of a study. This information helps people decide if they want to join or stay in the study. Informed consent is meant to protect participants and should give a person enough information to understand the risks of, potential benefits of, and alternatives to the study. In addition to the informed consent document, the process may involve recruitment materials, verbal instructions, question-and-answer sessions, and activities to measure participant understanding. In general, a person must sign an informed consent document before joining a study to show that he or she was given information on the risks, potential benefits, and alternatives and that he or she understands it. Signing the document and giving consent is not a contract. Participants may withdraw from a study at any time, even if the study is not over. See the Questions to Ask section on this page for questions to ask a health care provider or researcher about taking part in a clinical study.