Understanding Clinical Trials

It is important for potential participants in a clinical trial to understand what to expect before, during and after a research study.

Defining Clinical Trials

A clinical trial is conducted to evaluate the safety and efficacy of potential new medicines. In addition to assessing whether a medicine is safe and effective, clinical trials also determine whether the benefits of taking the medicine outweigh any potential side effects or negative reactions.

Before you agree to participate in a clinical trial, the study team will review the known or expected risks and benefits.

You will be asked to sign an agreement called an informed consent form (ICF). You should read the form carefully and ask any questions you have of the study doctor. You may choose to leave the study at any time after you sign this form. In some studies, you may receive a travel or participation stipend.

View frequently asked questions on this site for more information. For additional details about clinical trials, visit ClinicalTrials.gov or The Center for Information and Study on Clinical Research Participation.

Throughout the study period, you will be asked to take tests and complete procedures.

Some examples of these tests and procedures include giving blood or urine, taking X-rays, or measuring height and weight. Sometimes you will be asked to complete a study diary to share with the doctors any changes in your body or how you feel.

Each study is different and will be explained in the informed consent form. You should continue to receive care through your regular healthcare providers throughout the time you are participating in the study.

After the trial is completed, the study doctors will evaluate the results from all participants.

Anonymized results will be posted to ClinicalTrials.gov. Often the results from studies are published in medical journals as well, which can help improve care for people living with the condition that was studied.

As a participant in a clinical trial, you will be asked to participate over a certain time period. This could be days, months, weeks or even years. After that time, you may go back to your usual care, or in some cases you may be offered the opportunity to stay on the study medicine. It may take many years and many studies before a new medicine can be approved and used outside of a clinical trial setting.

What to Expect as a Parent or Caregiver of a Child

As a parent or caregiver of a child in a clinical trial, you will be asked to sign an informed consent form on the child’s behalf. In some cases, the study team will ask children to sign an assent form acknowledging their desire to participate. When deciding whether to enroll your child in a clinical trial, you may consider:

Asking your study doctor about what to expect each day you are in the hospital or clinic. For long study days, you may want to pack snacks, drinks and activities to pass the time.
Asking your study doctor if all of the tests and procedures will be completed at one location or if you will need to do a lot of walking or driving.
Asking the study team to help plan a schedule that works for you and your child. Usually you will stay with your child throughout the duration of a study visit.
Preparing your child for potential school absences. Work with your child’s teacher to create a plan to stay on track while participating in the study.
Answering any questions your child may have about going to the doctor. You might find a book to be a helpful way to find the right words to explain the process to them. Your study doctor may even have some recommendations on reading materials or how to address specific questions.

Clinical Trial Phases

A study medicine is assessed in people, often in volunteers without the condition, to evaluate its safety.
The study medicine is evaluated to determine optimal dosing. Phase 2 studies also offer early evidence of the potential effectiveness of a medicine.
The study medicine is evaluated, often in larger groups of people over a longer period of time, to determine its safety and effectiveness. Phase 3 studies often compare the study medicine to a placebo or approved treatment.
After a medicine has received regulatory approval, additional studies can offer insight into how the treatment is used.