Clinical Trials
Informed by recognized medical guidance
Overview
A clinical trial is a carefully planned research study that involves people. It helps doctors and researchers find out if a new treatment, test, or procedure is safe and works well. The results can lead to better ways to prevent, diagnose, and treat health problems.
Key facts
- Taking part is always voluntary. You can leave at any time without giving a reason.
- Every trial has a written plan (called a protocol) that explains its purpose, safety checks, and what will happen.
- Before joining, you will be told everything you need to know and asked to give informed consent — this means you understand the study and agree to take part.
- Trials are done in phases. Early phases focus on safety, while later phases test effectiveness and compare against current care.
Clinical trials are common around the world. Thousands of studies are running at any one time, and many hospitals and research centres take part.
Anyone can be invited to join a trial — healthy volunteers as well as people living with a specific health condition. Different trials include different age groups, including children and older adults, depending on what is being studied.
Symptoms
- Chest pain or trouble breathing
- Swelling of the face, lips, or tongue
- Sudden confusion, fainting, or seizures
- Weakness on one side of the body or difficulty speaking
- ⚠A high fever or a severe headache
- ⚠New or worsening side effects that worry you
- ⚠Any symptom the trial team told you to watch for
- ⚠An unexpected injury or illness during the trial
Common symptoms
- Extra clinic visits for check-ups and monitoring
- Blood tests, scans, or other medical tests
- Possible side effects from the treatment being tested
- A feeling of uncertainty, because you may not know which treatment group you are in
Symptoms in children
- A parent or guardian must give signed permission before a child can join.
- The trial team explains the study in a way the child can understand, and the child is asked if they are willing to take part.
- Visits and procedures are planned to cause as little disruption as possible to the child’s school and play time.
Symptoms in older adults
- The team will review other health conditions and medicines to check for interactions.
- Travel to trial visits may need extra planning, but some trials allow visits at different sites or offer support.
- Older adults are often encouraged to take part because results help improve care for older people.
Causes
Main causes
- To test whether a new treatment is safe and effective
- To compare a new treatment with the current standard of care
- To learn more about a disease and how it affects people
- To find better ways to prevent or detect health problems
Risk factors
- Your general health and other medical conditions (the trial team will review these)
- Medicines you already take, including over-the-counter products or supplements
- Being pregnant, trying to become pregnant, or breastfeeding (some trials exclude this to protect the baby)
- Having a condition that might make the experimental treatment riskier for you
When to see a doctor
See a doctor urgently if:
- Call your local emergency number immediately if you develop a serious or life-threatening symptom during a trial.
- Then contact the trial team as soon as possible and tell them what happened.
Book a routine appointment if:
- If you are thinking about joining a clinical trial, talk to your regular doctor or the research team before you decide.
- Bring a list of your questions about how the trial works, what will be expected, and what the possible risks are.
Diagnosis
There is no diagnosis involved in a clinical trial. Instead, the research team will do a screening to check whether you meet the trial’s requirements (called eligibility criteria). This usually happens before you are accepted into the study.
Tests that may be done
- Physical examination
- Blood and urine tests
- Imaging scans (such as ultrasound, X-ray, MRI or CT)
- Heart tracing (ECG) and other health checks
What to expect at your appointment
You will be given a plain-language information sheet and enough time to read it. You can ask the team any questions, and they will explain what will happen before, during, and after the trial. If you choose to join, you will sign an informed consent form. You will always be free to leave the trial at any time, without affecting your regular care.
Treatment
During the trial, you will receive the experimental treatment being studied, or a comparison treatment. The comparison treatment might be the current standard treatment or a placebo (a treatment that looks the same but has no active effect). The research team will monitor your health very closely and will tell you exactly what to do.
Self-care at home
- Keep a diary of any symptoms, changes, or concerns you notice between visits.
- Follow the trial instructions about how to take any treatment and when to come for appointments.
- Tell the trial team about every medicine, vitamin, supplement, or herbal product you use.
- Raise any worries with the team early — it is better to ask than to guess.
Medical treatments
Medical treatments in a trial can include a new medication (taken as a tablet, injection, cream, or infusion), a medical device, a therapy such as physical therapy, or a surgical procedure. All trials follow a strict, approved plan. You will always know what treatment you are receiving during the study, and you can ask for more details at any time.
When is surgery considered?
If a trial involves surgery, the research team will discuss the procedure in detail, including the risks and benefits. Surgical trials compare a new technique with the current standard operation, and you will be given time to make your decision.
Living with this condition
Being in a trial usually means you continue your daily life as before, but you need to set aside time for additional appointments and tests. You may need to follow extra instructions, such as recording symptoms or taking treatment at set times.
Lifestyle tips
- Maintain a regular routine and try to get enough sleep.
- Carry the trial team’s contact details with you.
- Tell other doctors or nurses you see that you are in a trial.
- Check with the research team before starting any new intense exercise.
Diet and exercise
Some trials have specific diet or exercise guidelines. If your trial does not, aim to eat a balanced diet and stay active in a way that feels comfortable for you. Always let the trial team know about any major changes to what you eat or how you exercise.
Mental health and emotional wellbeing
Taking part in a trial can bring hope, but it can also cause worry or stress. It is completely normal to feel this way. Talk to the research team, your regular doctor, or a trusted person about how you are feeling. You can also ask for help from a mental health professional if you need it.
Prevention
Clinical trials are not something you can prevent, but you can protect yourself by giving informed consent, asking questions, reporting side effects early, and following the study plan. Every ethical safeguard is in place, but no trial is completely free of risk.
Vaccines
Some trials test vaccines. If you join a vaccine trial, you will be told exactly what is in the trial vaccine and how it is monitored. It is still experimental, so the same consent and safety rules apply.
Screening programmes
Screening is a key part of joining a trial. The tests done during screening show whether the trial is safe for you and also provide a health baseline. This means the team can monitor any changes throughout the study.
Complications
If left untreated
- You may have side effects from the treatment being tested.
- The treatment may not help you, even if it helps other people.
- If the trial has a placebo group, you may not receive the active treatment.
- The extra visits and tests may take up more time than you expected.
Long-term outlook
Your participation helps researchers learn important information, whether the treatment works or not. This knowledge leads to safer and more effective treatments for future patients. Clinical trials are how medicine moves forward — every advance starts with someone who volunteered to take part. Remember, the research team is there to keep you safe and you can withdraw at any time.
Find support
International organisations
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Always verify with your doctor
Health guidelines vary by country and region. The information in this article is based on international clinical guidelines but may not reflect the specific guidelines, medications, or practices in your country. Always discuss your health concerns with your own doctor or healthcare provider, and refer to your local national health guidelines where available.
Important notice This information is for educational purposes only. It does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider about your specific situation. If you are experiencing a medical emergency, call your local emergency services immediately.
Related conditions
Sources and guidance
This article is educational and is prepared with reference to recognized health information and clinical guidance sources where available. Specific source links may vary by topic.
Last updated: July 31, 2026
Educational note: This information is for education only and is not a diagnosis.
Use it to support, not replace, advice from a licensed clinician.
If symptoms are severe, worsening, or urgent, call your local emergency number or seek emergency care.