About Clinical Trials

Every approved medicine is available because people volunteered to participate in a clinical trial.

Patients and healthy volunteers make priceless contributions to advances in medicine. They help us understand diseases and discover lifesaving and life-enhancing treatments.

What is a clinical trial?

A clinical trial is a research study. It is designed to test if a medicine, vaccine, or medical device is effective and safe. A clinical trial may take place at a hospital, doctors’ office, or clinical research center. It is conducted by doctors, nurses, and other healthcare team members.

Most ideas for a new medicine or treatment start in a laboratory. This is called "preclinical" research. Scientists research a new product in the lab, sometimes over many years, before testing it in people. 

Only the most promising treatments go on to be studied, or investigated, in human beings. People volunteer to test these investigational treatments in clinical trials. These studies are designed to find answers to very specific health questions. 

How your participation helps

Thousands of people volunteer to participate in clinical trials every year. The reasons for participation vary, but all of them help to advance medicine. Some reasons include:

  • Medical supervision. Some people have a disease for which there is no approved treatment. They might join a clinical trial in the hopes of receiving an experimental medicine.
  • Contribute to future treatments. Many participants wish to help future patients. This has been reported by both patients and healthy volunteers.
  • Help improve the lives of others. Some people participate with the hope of helping others. The investigational drug or vaccine could benefit other patients and, in some cases, save lives.

What to expect in a clinical trial

Clinical trials can take many years to develop and complete. Each one is designed differently. In general,

  1. Find out what kind of volunteers are being recruited to the study,
  2. Become informed about the specific details of the study, then determine whether you wish to give your consent to continue,
  3. Go through a screening process to find out if you are eligible to participate,
  4. If you are eligible, the study doctor and their staff will explain the study in detail and answer your questions. Their contact information will be included in your informed consent form.
1. Find out what kind of volunteers are being recruited

Researchers plan studies under specific conditions considering many different factors like age, gender, the type and stage of the disease, any previous treatments a patient received, and whether they have other medical conditions. 

To find out if you might qualify for a study, ask about:

  • Inclusion criteria: Factors that determine whether you can be included, and
  • Exclusion criteria: Factors that could prevent you from participating.
2. Understand what's involved before giving your consent

Before you decide to participate in a clinical trial, you will go through a process called "informed consent". This is designed to help you learn the facts about the clinical trial before deciding whether to participate. 

You will be given detailed information about the study. This includes: 

  • the purpose, 
  • the possible risks, 
  • the potential benefits, 
  • how long it will take,
  • what procedures are required, and 
  • whom to contact with any questions or issues. 

Once you understand this information, you may decide to participate. At that point, you will be asked to give your consent. You will need to sign an “informed consent” document to confirm your decision. 

Then, you will go through a screening process to find out if you qualify to participate in the trial, based on the inclusion and exclusion criteria.

3. Screening and enrollment

The screening process for a clinical trial is different for each study. It often involves a visit to the research facility (for example, a doctor's office or hospital), and an assessment by medical staff. During screening, you might find out that you are not able to enroll in the study. 

If screening shows that you can enroll, the clinical trial staff will walk you through the enrollment process and talk about logistics, like scheduling future visits.

Know your rights

An informed consent is designed to protect you. It is not a contract. You have a right to:

  • ask the research team questions at any time, and
  • stop participating in the clinical trial for any reason and at any time, even before the study is over.

Find out more

U.S. Food and Drug Administration. Inside Clinical Trials: Testing Medical Products in People. 


MAT-US-2105222-v1.0-10/2021 | Last update October 2021
Photo: Getty Images