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What is a Clinical Trial?

Clinical trials are part of clinical research and at the heart of all medical advances. Clinical trials look at new ways to prevent, detect, or treat diseases. Treatments might be new drugs or new combinations of drugs, new surgical procedures or devices, or new ways to use existing treatments. The goal of clinical trials is to determine if a new test or treatment works and is safe. Clinical trials can also look at other aspects of care, such as improving the quality of life for people with chronic illnesses.


Who participates in Clinical Trials?

Many different types of people participate in clinical trials. Some are healthy, while others may have illnesses. A healthy volunteer is a person with no known significant health problems who participates in clinical research to test a new drug, device, or intervention. Research procedures with healthy volunteers are designed to develop new knowledge, not to provide direct benefit to study participants.

A patient volunteer has a known health problem and participates in research to better understand, diagnose, treat, or cure that disease or condition. Research procedures with a patient volunteer help develop new knowledge. These procedures may or may not benefit the study participants.

Patient volunteers may be involved in studies similar to those in which healthy volunteers participate. These studies involve drugs, devices, or interventions designed to prevent, treat, or cure a disease.

All clinical trials have guidelines about who can participate, called inclusion/exclusion criteria. Factors that allow someone to participate in a clinical trial are “inclusion criteria.” Those that exclude or do not allow participation are “exclusion criteria.” These criteria are based on factors such as age, gender, the type and stage of a disease, previous treatment history, and other medical conditions. Before joining a clinical trial, a participant must qualify for the study. Some research studies seek participants with illnesses or conditions to be studied in the clinical trial, while others need healthy volunteers. Some studies need both types.


Inclusion and exclusion criteria are not used to reject people personally; rather, the criteria are used to identify appropriate participants and keep them safe, and to help ensure that researchers can find new information they need.

What is the next step after I find a Clinical Trial?

Once you find a study that you might want to join, contact the clinical trial or study coordinator. You can usually find this contact information in the description of the study. The next step is a screening appointment to see if you qualify to participate. This appointment also gives you a chance to ask your questions about the study.


Let your doctor know that you are thinking about joining a clinical trial. He or she may want to talk to the research team about your health to make sure the study is safe for you and to coordinate your care while you are in the study.

What questions should I ask before deciding if I want to take part in a Clinical Trial?

If you are offered a clinical trial, feel free to ask any questions or bring up any issues concerning the trial at any time. The following suggestions may give you some ideas as you think about your own questions.

The Study

  • What is the purpose of the study?

  • Why do researchers think the approach may be effective?

  • Who will fund the study?

  • Who has reviewed and approved the study?

  • How are study results and safety of participants being checked?

  • How long will the study last?

  • What will my responsibilities be if I participate?

Possible Risks and Benefits

  • What are my possible short-term benefits?

  • What are my possible long-term benefits?

  • What are my short-term risks, such as side effects?

  • What are my possible long-term risks?

  • What other options do people with my disease have?

  • How do the possible risks and benefits of this trial compare with those options?

Participation and Care

  • What kinds of therapies, procedures, and/or tests will I have during the trial?

  • Will they hurt, and if so, for how long?

  • How do the tests in the study compare with those I would have outside of the trial?

  • Will I be able to take my regular medications while participating in the clinical trial?

  • Where will I have my medical care?

  • Who will be in charge of my care?

Personal Issues

  • How could being in this study affect my daily life?

  • Can I talk to other people in the study?

Cost Issues

  • Will I have to pay for any part of the trial, such as tests or the study drug?

  • If so, what will the charges likely be?

  • What is my health insurance likely to cover?

  • Who can help answer any questions from my insurance company or health plan?

  • Will there be any travel or child care costs that I need to consider while I am in the trial?

Tips for Asking Your Doctor About Trials

  • Consider taking a family member or friend along for support and for help in asking questions or recording answers.

  • Plan ahead what to ask, but don’t hesitate to ask any new questions you think of while you’re there.

  • Write down your questions in advance to make sure you remember to ask them all.

  • Write down the answers, so that you can review them whenever you want.

  • Ask about bringing a tape recorder to record what’s said (even if you write down answers).

This content is brought to you by the National Institutes of Health (NIH).


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