Each clinical trial has its own set of “eligibility criteria,” which consists of two groups:

1) Inclusion criteria – characteristics a patient must have to participate in a clinical trial.

2) Exclusion criteria – characteristics that exclude a patient from participating in a particular clinical trial.

Eligibility criteria may include age, sex, location, disease state, and health status.

The best way to see if you meet the eligibility criteria to participate in a study is to view the criteria on clinicaltrials.gov or the study website.

No. However, if you have health insurance, you should check with your health plan to see what may be covered, as some health plans may cover research-related expenses. Conversely, some clinical trials do not involve health insurance, making them beneficial to underinsured or uninsured patients.

Clinical trials are typically paid for by the sponsor of the clinical trial. Each clinical trial is different; however, it is common for the sponsor to cover all research-related expenses, including medication(s), exams, tests, and sometimes travel reimbursement expenses. Additionally, some clinical trials may compensate participants for their time and travel.

There are four phases of a clinical trial. Phases I, II, and III clinical trials enroll patients, pre-FDA approval, to ensure the safety and efficacy of new treatments. Phase IV clinical trials phase occurs post-FDA approval and does not enroll patients into a program; instead, it tracks data of the newly approved drug.

    • Phase I is utilized to test a new treatment’s safety and identify side effects. Treatments are given to a small group, commonly between 20-80 people.

    • Phase II is utilized to test the efficacy, and additional safety, of a new treatment. Treatments are given to a larger group, commonly between 100-300 people.

    • Phase III compares the new treatment to similar, approved treatments to test efficacy, monitor side effects, and collect data. This information is used to guide how the treatment can be used safely. Treatments are given to large groups, commonly between 1,000 and 3,000 people.

    • Phase IV is utilized to track the new treatment’s safety within the general population after it has been approved by the U.S. Food and Drug Administration (FDA). This is also used to continue the collection of data about the new treatment’s side effects, benefits, and best use. The FDA approves treatments in this phase and are available through health care providers.

Control groups are a crucial function in determining the effectiveness of a new treatment. Control groups are compared to groups that receive the studied treatment to assess the efficacy of the new treatment. The clinical trial will note the type of control group they are utilizing in the study design (the set of methods and procedures used to collect and analyze data in a study). There are several types of control groups, detailed below:

    • Placebo Concurrent Control Group – the most commonly used control for clinical trials. Participants are randomly assigned to either receive the new treatment or a placebo. (Learn more about what a placebo is below) The group receiving the placebo is the control group.

    • Active (Positive) Concurrent Control – participants are randomly assigned to receive a comparable current treatment or the new treatment. The group receiving a comparable treatment is the control group.

    • Dose-Response Concurrent Control – participants are randomly assigned to receive a “fixed dose” of the new treatment or to a group(s) that gradually increases dosage throughout the trial. The group receiving the “fixed dose” is the control group.

    • No Treatment Concurrent Control – participants are randomly assigned to one of two groups, “no treatment” or “treatment.” The group receiving “no treatment” is the control group.

A placebo is an inactive substance with no therapeutic effect administered to a patient in a clinical trial the same way the trial medication is administered. For example, if the trial medication is administered via two capsules, the placebo will also be administered via two capsules; however, it will have an inactive substance. Placebos allow researchers to compare the results of these two groups and determine if the therapeutic changes in the test group result from the treatment or by chance.

Study participants are assigned to either receive the medication being tested or to a control group through a process called “randomization.” Participants will not know which group they were randomly assigned to during the trial. This is also called a single-blinded study, where the researchers know what the patient is receiving; however, the patient is not. Additionally, some trials may be double-blinded, meaning that in addition to the patient not knowing which group they are in, the research team also does not know during the trial which groups the participants are in.

Yes. You can disenroll from a clinical trial at any time.

Clinical trials come with many benefits, but along with those benefits, there are also risks. Participation in a clinical trial requires an important conversation with your health care provider and support team to determine if the benefits outweigh the risks for you.


    • Access to the newest treatments.

    • Alternative treatment options for those who have not responded to current medications.

    • The opportunity to help others who suffer.

    • Opportunities for one-on-one discussions with experts.


    • Participants are not guaranteed to be treated with the new treatment,

    • It can be a time-consuming process.

    • While uncommon, study participants may experience serious or life-threatening complications from the new treatment.

Clinical trials are overseen by the United States Food and Drug Administration (FDA).

“Protecting the rights, safety and welfare of people who participate in clinical trials is a critical aspect of the FDA’s mission. FDA oversees clinical trials to ensure they are designed, conducted, analyzed and reported according to federal law and good clinical practice (GCP) regulations.” – FDA

All clinical trials have safeguards in place to protect patients. These include:

    • The Protocol Review Process

    • Informed Consent Procedures

    • The Patient Representative

    • The Patient Bill of Rights

To learn more about these safeguards, visit https://clinicalcenter.nih.gov/participate/faqaboutcs.html.