How clinical trials work

What is a clinical trial?

Clinical trials are research studies that test if a new potential therapy is safe and effective for patients. They evaluate new drugs, behaviors, or devices, and reveal whether these potential therapies work for particular illnesses or particular groups of patients. Clinical trials provide the best available data with which to make healthcare decisions, and are considered the gold standard in the development of new therapeutic options.

There are two main types of clinical trials: interventional studies and observational studies:

  • Interventional studies. These are clinical trials testing whether a specific intervention (such as a drug, device, or behavioral change) affects health-related outcomes. Different groups of people are assigned at random to receive and not receive the intervention in a process called randomization. Typically the group that does not receive the intervention — also known as the control arm — receives either the current standard of care or a placebo (a fake version of the intervention), depending on the condition. It's important to note that trials for life-threatening conditions, such as cancer, will rarely offer a placebo. Interventional trials are also typically blinded, meaning that the volunteer is not aware if they are in the control group or receiving the intervention, or double blinded, meaning that both the researcher and the volunteer are not aware.
  • Observational studies. These studies, on the other hand, are ones in which participants are put in groups based on their characteristics, and an intervention is tested in each of these groups. The difference is that the groups are assigned based on volunteer characteristics, rather than at random. Both types of studies follow a protocol, a detailed plan for the study written by the trial sponsor and approved by the FDA.

A trial sponsor is an organization which initiates, funds, and conducts a clinical trial. This is often a pharmaceutical company, but it can also be a university or another type of research organization. When selecting a clinical trial, it's important that potential volunteers are fully aware of and comfortable with who is sponsoring the trial.

Potential volunteers for trials can be anyone. While many people view clinical trials as a last resort only to be relied upon when all other options have been exhausted, this is not the case; research studies need a variety of participants to enroll. Some trials are looking for volunteers who have been recently diagnosed, while others may be only need those who have been living with a condition long-term. Certain studies may require patients who have had different treatment experiences in the past. Every trial is different, but with thousands of studies recruiting, there is likely a trial that is right for you.

What are the phases of clinical trials?

Clinical trials begin with an idea in a lab. Researchers thoroughly test potential treatments in the lab and in animals before ever beginning trials in humans. If these lab and animal tests are successful and the therapy looks promising, the researchers will begin to conduct research studies beginning at Phase 1 and moving through to Phase IV:

  • Phase I clinical trials test whether drugs are safe to use in humans.
  • Phase II clinical trials test the effectiveness of a drug or medical device. This stage can last from several months to a few years, and generally involves several hundred participants.
  • Phase III clinical trials are typically the largest. They involve anywhere from several hundred to several thousand participants in a randomized, blind study. This testing phase can last several years as the FDA gathers thorough data about the drug's effectiveness and potential side effects.
  • Phase IV trials, also known as Post Marketing Surveillance Trials, take place after a drug or device has been approved. In this phase, pharmaceutical companies monitor a drug's long-term effectiveness and impact, compare it to existing trials in the market, and determine the cost effectiveness of the new treatment.

It's a big decision to take part in a clinical trial, and it's important that patients and caregivers fully understand all of the benefits and risks before enrolling. We'll discuss these in the next section.

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Why join a clinical trial

There are many reasons that people choose to volunteer for clinical research, but it's important to weigh these against potential risks. Some of the top benefits of taking part in research include:

Access to care. People who take part in a clinical trial receive access to the latest treatments in development, and for many patients looking for options, this is a real benefit. In fact, according to a CISCRP survey of 2,194 former clinical trial participants, 44% of people surveyed cited "obtain better treatment" when asked to share their top reasons for participation. In some cases, patients are able to continue taking the drug after the trial is over, as well. And, in many cases, patients receive either the standard of care or the investigational drug, removing the risk of receiving a placebo.

Quality of care. Patients in clinical trials report a high level of personalized care while participating in research. While trials may require more office visits than normal, or more tracking of symptoms, this extra time spent on health can mean a higher quality of care.

Financial benefits. Treatments administered during a clinical trial are often given at no cost to patients; in fact in many cases, volunteers are compensated for their time, travel, or participation in general. The amount of payment has to do with the phase of the trial - earlier trials such as Phase 1 pay more (nearly $2,000 on average) because the treatments being studied are less well-understood. To find a paid clinical trial, you'll likely need to find a few trials for which you may qualify, then contact the sites to learn about potential payment.

Helping advance science for future generations. The goal of clinical trials is to discover new, better treatments (and cures) for the condition being studied. This means that, if successful, patients with that condition in the future will have better options than current patients, and this is an important motivator for many patients today. In the CISCRP survey referenced above, nearly half of participants cited "help advance science, treatment of disease/condition" as one of their top reasons for participation.

On the other hand, of course, clinical trials also come with some degree of risk. There is chance that the treatment being studied might not work as expected or be a better option than the standard of care. The study drug could also cause an unexpected side effect, especially in earlier phase trials.

With that said, there are several protections in place for patients who take part in clinical trials:

  • An Institutional Review Board (IRB) ensures that trials are ethical and that participant rights are protected, and the FDA provides oversight for all clinical trials testing new drugs or devices.
  • Participant rights include informed consent, meaning that volunteers are given all the facts about a trial and can ask any questions they'd like before enrolling. These questions might include:
    • How long will the study last?
    • What is the goal of the study?
    • Will I be reimbursed for my expenses?
    • Does the study include a placebo?
    • How will I receive the treatment?
    • Can I continue taking the study drug after the trial if it works for me?
    • How will my privacy be protected?
    • What can I expect at each study visit?
    • What happens if I leave the study early?
    • What happens if my condition gets worse or I am injured during the trial?
    • Who will be conducting the study?
    • What did previous studies find out about the treatment? Have the results been published?
    • What are the potential risks and benefits of the study drug?
    • Will I receive follow-up care after the study?
    • Will the results of the trial be provided to me?
  • After signing an informed consent, a participant can still leave a clinical trial at any time, during any reasons. In addition, if unexpected risks emerge during the trial, patients have a right to be informed about that and removed from the study if appropriate.
  • Special protection is also given to children who participate in trials as well. Often, both parents must give legal consent, and children over age six need to agree to take part as well.

Before making the decision to join a clinical trial, it can be helpful to hear from someone who's taken part in it. Emily Schaller, founder and CEO of the Rock CF Foundation, talked with Antidote about her experience participating in several clinical trials for cystic fibrosis, a progressive lung condition that she has lived with since she was 18 months old, in the below video. 

What It's Like to Participate in a Clinical Trial from Antidote Technologies on Vimeo.

How to find a clinical trial

To find a clinical trial, you can use a clinical trial search tool, such as or Antidote, or ask your doctor about opportunities they know of. If you do start your own online research, you can also bring options you're interested in to your doctor. is a government website where all clinical trials are registered. It is comprehensive, but was built for researchers rather than patients. To search for clinical trials in your area, you can enter in your condition and location in their search box.

Antidote created a search tool designed with patients in mind. It pulls in listings from, but organizes the trials by their inclusion and exclusion criteria so that patients can find a trial that they may qualify for just by answering a few questions. To use Antidote's match tool and find a clinical trial that may be a match for you, start by following these steps:

  1. Enter your basic information. To start, enter your condition, zip code, and age to start narrowing down your trial options.
  2. Next, choose how far you're willing to travel for a clinical trial. To see all of your options in the United States, choose "any" as the distance you're willing to travel.
  3. Answer a few questions about your medical history. Depending on the condition you chose in the first step, Antidote may ask you a few questions about the medications you're taking, if you live with any other conditions, and other related questions. Each clinical trial has specific inclusion and exclusion criteria. This step helps narrow down your options to find trials for which you may qualify.
  4. View your results and click into a trial to learn more. After answering a few questions, you'll reach your trial results page. To learn more about a particular trial, click on the trial's name. On individual trial pages, you'll find information about what intervention the trial is researching – a potential new drug, an exercise regime, a medical device, etc. – what stage the trial is, and the inclusion and exclusion criteria for the trial.
  5. If you're interested in a trial, reach out to the trial team. Find the trial's site location that's closest to you, and click "Choose This Site." You'll then have the opportunity to view the site's details and email them to yourself. After you contact the study site by email, the study team will get in touch to learn more about you. If they determine based on your phone screening that you may qualify for the trial, you'll be invited for an in-person screening.
  6. Talk to your doctor. Share trials you're interested in with your primary care physician or specialist. They can advise on whether they believe the trial is a good option for you considering your current treatment plan.

Emily of Let's Rock CF also shared how she found the clinical trials she participated in, and offers tips on searching for one that's right for you.

How to Find Clinical Trials from Antidote Technologies on Vimeo.

What to expect when you join a clinical trial

After you've expressed interest in a clinical trial by contacting the trial team or filling out a pre-screener online, what comes next?

Exact experiences vary, but your trial experience will most likely follow these steps:

Phone screening: After you've found a clinical trial you're interested in and reached out to the trial team, or completed a pre-screener online, the trial team will give you a call to ask you a few more questions and learn more about you. If they determine based on the phone screening that you may be a good fit for the trial, you'll be invited for an in-person screening at the study site.

In-person screening: At the in-person screening, doctors associated with the trial will ask you more questions, and you may be given a physical. You may also be asked to complete additional medical tests to ensure that the study is right for you. If the trial requires multiple tests, you may be asked to come in for a second visit. If the study team determines that you're qualified for the trial, you'll be invited to join.

Informed consent: Next, the trial team will answer all of your questions and go over the details of the trial. Be sure to ask any questions you'd like such as how the long the trial will last, what you can expect from each study visit, and whether you will be reimbursed for your expenses or receive additional compensation. Next, you'll be asked to sign an informed consent form to officially join the trial.

Study visits: The study visits themselves will vary based on the kind of trial it is. Your visits may be similar to regular doctor's appointments, with additional attention and questions related to the clinical trial. For some trials, site visits are conducted virtually. In those trials, you'll talk with the study team over a webcam on your computer or a device provided by the trial.

In between visits: Some trials may also ask you to keep a virtual or paper diary during the trial to track your symptoms or answer other questions related to your health, such as your exercise routine. It's important to record your diary entries as directed by the study team to ensure that the study is collecting accurate data.

After the trial: You may be able to continue taking the study drug after the end of the trial – the study team should let you know before you join, but ask if they don't mention it. You can also ask before the trial starts how you can see the results of the study after it's completed. Trial teams publish their results, so you should be able to find the study after it's complete, even if it's not directly shared.

doctor showing tablet to patient

Frequently asked questions

Q: Will I be compensated for participating in a clinical trial?

A: Some clinical trials will cover your travel expenses and other expenses you may incur from participation. Other trials also offer additional compensation. Earlier stage trials are more likely to be paid, but Phase II and Phase III trials can sometimes offer compensation, too. Ask the study team before joining.

Q: What if I'm rejected from a clinical trial I'm interested in?

A: Every clinical trial has unique inclusion and exclusion criteria. If you don't qualify for one trial you're interested in, you may qualify for another in your area. You can also sign up for alerts from Antidote to hear about new trials that match your profile.

Q: What if I receive a placebo?

A: A placebo is a medication without any therapeutic effect that's used to compare against a study drug. Not all trials use placebos – for example, cancer trials rarely use them. Some trials measure a study drug against the standard of care for that condition, or against another treatment. Depending on the trial, you may be able to stay on your current medication, too.

Q: Will I be able to stay on the study drug after the trial is complete?

A: In some trials, you are able to continue taking the study drug at the end of the trial. Ask the study team before you join the trial.

Q: Can I quit a clinical trial once it starts?

A: Yes, even after you sign your informed consent form, you can still leave a clinical trial at any time, for any reason.

Q: How much time does it take to participate in a clinical trial?

A: Time commitment varies across clinical trials. While some trials may include weekly site visits or overnight stays, others may only require short visits every few weeks or months. Make sure you find out about time commitment as part of the informed consent process.

Medical research can't move forward without clinical trial volunteers. If you're ready to get involved, start searching for a trial that matches you below.

Search for a Clinical Trial Near You

It just takes a few minutes to find clinical trial opportunities in your area that could be a fit for you. Start searching and find your clinical trial match.

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