In this article you will learn:
- What informed consent means and why it is required before any trial procedure
- What happens at each step, from screening to signing the consent form
- What information the patient information sheet and consent form must contain
- What the three basic conditions for valid consent are
- How consent works for people who cannot decide for themselves
- What rights stay with you after you sign, including the right to withdraw
- What to do if something changes during the trial or something goes wrong
What is informed consent in a clinical trial?
Informed consent is the process by which a person voluntarily confirms their willingness to take part in a research study, after being informed of all aspects of the study relevant to that decision. It is an ongoing process, not a one-off event: it involves giving information, discussing and clarifying it, obtaining written consent, and later sharing any new information that could affect a person's willingness to continue[1]. This staged structure exists precisely because a single conversation, however thorough, cannot capture everything a participant needs to know across weeks or months of trial participation. The information given should cover the purpose of the research, what taking part will involve in practice, the possible benefits and risks, and the alternatives available, so that the decision is grounded in the participant's own situation rather than in general assumptions about the trial[2].
The patient's informed consent is a necessary condition for taking part in any clinical trial procedure — no study activity can start before it is given. A clinical trial must be conducted so that the rights, safety, health and well-being of participants take priority over the interests of science and society. This principle sets the order of priorities for everyone involved in a trial: investigators, sponsors and ethics committees are all expected to treat the participant's welfare as the standard against which every other decision is measured[3].
What happens before you are asked to sign anything?
Before formal enrolment, patients interested in taking part go through a screening process. Details of a person's medical condition — such as age, gender, disease type and stage, and previous treatment history — determine whether they meet the trial's inclusion and exclusion criteria. This screening is carried out before any detailed discussion of consent, because there is little point in explaining the full trial protocol to someone who, for medical reasons, could never actually take part in it[2].
- Initial questionnaire — potential participants usually complete a short questionnaire to check basic eligibility[2];
- Further screening — those who meet the initial requirements are invited for a more detailed assessment, usually with a doctor or other healthcare professional directly involved in the trial[2];
- Consultation — once screening confirms eligibility, the patient has a consultation where detailed information about the trial is given, questions can be asked, and informed consent is signed or refused[2].
This sequence matters because it separates the question of whether a person is medically suitable for a trial from the separate question of whether they understand and freely accept what participation would involve. Only once eligibility is confirmed does the conversation move on to the substance of consent itself. Each of these steps also gives the potential participant a natural point at which to step back, ask further questions, or decide not to continue, without having to justify that choice to anyone[2].
Who is allowed to ask for your consent?
It is the responsibility of the chief investigator or sponsor to create the informed consent form, following templates such as those provided by the Health Research Authority. The principal investigator is responsible for the conduct of the consent process but can delegate this task to another suitably qualified member of the research team[1].
For clinical trials of an investigational medicinal product, the person delegated to obtain consent must hold valid Good Clinical Practice (GCP) certification, and only individuals named on the site's delegation log may obtain informed consent from participants. In obtaining and documenting consent, the research team must comply with GCP and with the ethical principles set out in the Declaration of Helsinki. This chain of accountability — sponsor, chief investigator, delegation log — is designed so that a participant always knows exactly who is authorised to speak to them about the trial and who can be held responsible for the quality of that conversation. Because GCP certification and delegation logs are checked and audited, a participant who has doubts about whether the right person is taking their consent can, in principle, ask to see confirmation of that person's role[1].
What information must you receive before deciding?
The principal investigator or delegate is responsible for providing a written participant information sheet, approved by the reviewing ethics committee and the study sponsor, written in lay terms that are easy to understand. The recommended format follows a question-and-answer structure[1].
Guidance from the Spanish Agency for Medicinal Products and Medical Devices (AEMPS) sets out what a model patient information sheet should contain, including sections on voluntary participation, the study objective, and study activities. The document should not exceed 15 pages, including the consent form itself, and should avoid unexplained technical terms. This page limit and plain-language requirement exist to stop the information sheet becoming a legal shield rather than a genuine communication tool, since a document nobody reads in full cannot support a genuinely informed decision. The same guidance also recommends that the information be organised so that a participant can find the answer to a specific question quickly, instead of having to read the entire document to understand a single point, such as how many visits are involved or what happens if a test result is abnormal[4].
| Section of the information sheet | What it must tell you |
|---|---|
| Voluntary participation | Why you are being invited; that participation is voluntary and consent can be withdrawn at any time without affecting your relationship with your doctor or your treatment[4] |
| Study objective | The main question the trial is trying to answer, in plain terms, without technical detail about mechanism of action[4] |
| Study description | A description of who the study is aimed at, the total number of participants planned, the drug(s) involved, the number of treatment groups, and the chances of receiving the study drug versus a comparator[4] |
| Randomisation and blinding, in plain language | That assignment to a group is done "at random", and, for double-blind studies, that "neither the doctor nor the patient will know what treatment you will receive" — without using the word "randomisation" itself[4] |
| Placebo, if used | An explanation that a placebo looks like the study drug but contains no pharmacologically active substance and is not expected to have an effect[4] |
| Study activities | The duration of the study, with the treatment phase separated from the follow-up phase, and the number and frequency of visits and tests[4] |
What are the three conditions for consent to be valid?
Consent is only valid when three conditions are met together: the person has all the necessary information, has the capacity to consent, and gives consent voluntarily. None of the three is sufficient on its own. A person could be fully informed and legally capable, yet still be pressured, and the consent given in that situation would not be valid[5].
- You must have all the information — you should receive a patient information leaflet written in plain language explaining the study, its risks and benefits, and you must have the chance to ask questions[5];
- You must have capacity to consent — capacity means being able to understand, remember and weigh up the information given, and then communicate your decision to the research team; the law assumes an adult has capacity unless shown otherwise[5];
- You must give consent voluntarily — you choose to consent without feeling pressure from anyone, including family, friends, or your own doctor or nurse[5].
The principal investigator or delegate must allow the participant adequate time to decide whether to take part; ideally, the participant should be able to take the information sheet away to consider it before deciding[1]. The patient is entitled to sufficient time to carefully read the written trial information and the consent form before signing[3]. Taken together, these three conditions mean that a rushed signature obtained in a busy clinic, without a real opportunity to think things over, cannot on its own be treated as valid consent, whatever the paperwork says[5].
How is the consent form actually signed?
Best practice is for the consent form to have each statement initialled by the participant, rather than simply ticked. The consent form must always refer to the current, sponsor-approved version of the patient information sheet, with the correct version and date recorded. Initialling each statement individually, instead of a single tick or signature, forces both the participant and the person taking consent to slow down and confirm that each specific point — from the risks to the right to withdraw — has actually been addressed[1].
Under the ICH E6 guideline, consent is described as a three-step process, and can take the form of a paper document, an electronic (e-consent) format, or other valid formats. A remote, video-conference consultation can also be used, allowing questions and answers, as an alternative to a face-to-face meeting. This flexibility around format reflects the same underlying principle in every case: the medium used to record consent matters less than whether a genuine two-way conversation actually took place before signature. Whether the form is signed on paper, confirmed electronically, or agreed verbally after a video call, the record kept afterwards must still show clearly what the participant was told and what they agreed to[6].
After signing, the patient has the right to receive a copy of the written trial information and of the informed consent document, signed by both the patient and the physician[3].
Is consent always given in writing?
Some studies ask for consent in writing, while others accept verbal consent, depending on the type of study[5]. For some low-risk trials comparing medicines that are already approved and prescribed as part of routine care, a proposal exists to record consent directly in the participant's medical record instead of a separate written consent form, while keeping the legal requirement that informed consent must still be sought beforehand[7].
In that low-risk scenario, the prescriber still has a conversation with the potential participant, discusses the information sheet, and explains the benefits and risks, why the trial is happening, how data will be used, and how to withdraw consent later. What changes is the paperwork, not the substance of the conversation itself: the same information must still be shared and understood before any record is made. The approach for other, higher-risk types of clinical trials is not proposed to change. This distinction between low-risk and higher-risk trials reflects a proportionate approach: the more a trial departs from standard care, or the greater the uncertainty about the intervention, the more formal and detailed the consent documentation is expected to be[7].
What happens if you cannot give consent yourself?
If a person is not able to provide consent themselves, legal arrangements exist to help determine who is involved in consent decisions on their behalf. A two-stage capacity assessment can be used by the research team to decide whether a person has the capacity to consent, if there are concerns about this[5].
Special attention is also given to how information and consent materials are designed for children and young people: youth advisory groups review the language, terminology, design and age-appropriateness of information sheets, consent forms, and assent forms used in paediatric trials. The distinction between consent and assent is deliberate: a child too young to give legally binding consent can still be asked, in language suited to their age, whether they agree to take part, and their views are taken into account alongside those of a parent or guardian[6]. This layered approach — capacity assessment for adults who may lack it, and age-appropriate assent alongside parental consent for children — is meant to make sure that a person's inability to sign a standard consent form never simply removes them from the decision-making process altogether[5].
What rights do you keep after you have signed?
Consent is an ongoing process: participants must continue to receive any new information that could affect their willingness to keep taking part[1]. Signing the form is not the end of your involvement in decisions about the trial.
- You have the right to withdraw your informed consent and stop taking part at any time, without giving a reason[3];
- You have the right to contact the principal investigator, ask questions, and report any noticeable change in your well-being[3];
- You have the right, at each stage of the trial, to be informed about your health status and to inspect the records concerning you[3];
- You have the right to receive information about any new data that may affect your decision on continuing to take part[3];
- You have the right to protection of your personal data[3].
Refusing to take part, or withdrawing later, does not involve any consequences for the participant and does not result in the loss of treatment rights. This is the practical proof that consent given at the start of a trial was genuinely voluntary: a participant can change their mind at any later point, for any reason or none, without having to fear that their ordinary medical care will suffer as a result[3].
What happens if you are harmed while taking part?
A participant has the right to seek compensation if they suffer permanent damage to their health because of the investigational product or a medical procedure required by the trial protocol. The sponsor covers the cost of the investigational product, of medical care linked to the trial protocol, of specialised tests carried out to qualify the participant for the study, and of the treatment of certain adverse reactions[3].
In Poland, a Clinical Trials Compensation Fund provides financial support to a participant who has suffered injury as a result of taking part; claims are submitted to the Patient Ombudsman and can be granted for injuries suffered in trials that began after 14 April 2023. Participants can also be reimbursed for documented expenses incurred because of the trial, such as travel costs. Mechanisms of this kind exist because informed consent is meant to shift decision-making power to the patient, not to shift financial or medical risk away from the sponsor. Knowing in advance who bears the cost of an adverse event, and how a claim can be made, is itself part of the information a participant needs before they can be said to have consented with full understanding of what taking part actually involves[3].
What should you tell the research team, and when?
Once enrolled, it is the participant's responsibility to inform the investigator about their current state of health and about any side effects or noticeable changes in well-being. If you plan to change or cancel a scheduled appointment, you should inform the investigator or the study centre in advance where possible[3].
Consent also covers sharing your medical records with the research team, sponsor representatives, inspectors or auditors, and the trial results collected during the study. You should take the investigational medicine only as directed by the principal investigator and should not pass it on to anyone else. These obligations are the practical counterpart to the rights described earlier: consent creates a relationship of mutual responsibility between the participant and the research team, not a one-sided permission slip. Meeting these small, ongoing obligations — turning up, reporting changes, following dosing instructions — is what allows the safety and compensation systems described above to actually work as intended[3].
When should you speak to the research team before deciding?
You should speak to the research team before signing if you do not fully understand any part of the information sheet, the objective of the study, what will happen at each visit, or what a placebo or randomisation means in your specific trial[4]. You are entitled to take the information sheet away and consider it before making a decision, rather than deciding on the spot[1].
After you have joined a trial, contact the principal investigator if you notice any change in your health, if you have a question about a procedure, or if new information is shared with you that makes you reconsider taking part — you have the right to have all of this answered and to withdraw at any point. None of these questions need to wait for a scheduled visit: raising a concern as soon as it arises is part of what keeps the consent you gave at the start still valid as the trial goes on[3].
Summary
Informed consent is a structured, staged process built around one goal: making sure you decide freely, with full understanding, before anything happens to you as part of a trial[1]. It starts with screening against eligibility criteria, continues through a detailed consultation and a plain-language information sheet, and results in a signed — or refused — consent form. You are always entitled to take time over that decision and to take the paperwork away to read[3].
Signing is not the end of the process. You keep the right to ask questions, to be told about your health status and any new information, to have your data protected, to seek compensation if you are harmed, and to withdraw at any time without giving a reason and without losing access to treatment. If anything about the trial changes, or if you notice a change in your own health, telling your research team is both your right and part of how the process is designed to keep working for you[8].
❓ Can I withdraw my consent after I have already signed the form?
Yes. You have the right to withdraw your informed consent and discontinue participation in the trial at any time, without giving any reason. Refusing or withdrawing does not involve any consequences and does not result in the loss of your treatment rights.
❓ Who is allowed to go through the consent process with me?
The principal investigator conducts the consent process but can delegate it to another suitably qualified team member. For trials of an investigational medicinal product, that person must hold a valid Good Clinical Practice certificate and be named on the site's delegation log.
❓ Do I have to sign the consent form immediately?
No. You should be given adequate time to decide. Ideally, you can take the patient information sheet away to consider it before signing, and you are entitled to sufficient time to carefully read both the trial information and the consent form.
❓ What if I cannot understand or make the decision myself?
If you are not able to provide consent yourself, legal arrangements determine who is involved in the decision on your behalf. A two-stage capacity assessment can be used by the research team if there are concerns about your ability to understand, remember and weigh up the information.
❓ Is consent always given on paper?
No. Consent can be given in writing, verbally, or electronically (e-consent), depending on the study and its risk level. For some low-risk trials comparing already-approved medicines, a proposal exists to record consent in the medical record instead of a separate written form, while still requiring that consent be sought beforehand.
❓ What happens if I am harmed while taking part in the trial?
You have the right to seek compensation for permanent health damage caused by the investigational product or a required study procedure. The sponsor covers costs of the investigational product, related medical care, qualifying tests, and treatment of certain adverse reactions. In Poland, a Clinical Trials Compensation Fund supports participants harmed in trials starting after 14 April 2023.
❓ What should I tell the research team once I have joined the trial?
You should inform the investigator about your current state of health and any noticeable changes or side effects. You should also tell the study centre in advance if you need to change or cancel a scheduled appointment, where possible.
- [1] Informed consent (clinical trials) procedure - Rotherham Doncaster and South Humber NHS Foundation Trust (RDaSH) (accessed 2 June 2026) — https://www.rdash.nhs.uk/policies/informed-consent-clinical-trials-procedure/
- [2] Trial Participants: Informed Consent, GCP, Patient Involvement: The Next Steps (accessed 2 June 2026) — https://learning.eupati.eu/mod/book/view.php?id=346&chapterid=297
- [3] Charter of rights and obligations of a clinical trial participant - Agencja Badań Medycznych (ABM) (accessed 2 June 2026) — https://abm.gov.pl/download/1/8523/Charterofrightsandobligationsofaclinicaltrialparticipant.pdf
- [4] Guideline for correct preparation of a model patient information sheet and informed consent form (PIS/ICF) - Annex VIIIA, Spanish Agency for Medicinal Products and Medical Devices (AEMPS) (accessed 2 June 2026) — https://www.aemps.gob.es/en/investigacionClinica/medicamentos/docs/annex8a-Ins-AEMPS-EC.pdf
- [5] Consent - Be Part of Research, NIHR (accessed 2 June 2026) — https://bepartofresearch.nihr.ac.uk/taking-part/Consent/
- [6] Houyez F. Informed consent of trial participants. Session 2: ICH E6(R3) main changes - Informed consent. ACT EU workshop on ICH E6(R3), EMA, Amsterdam, 19-20 February 2025 (accessed 2 June 2026) — https://www.ema.europa.eu/en/documents/presentation/presentation-session-2-informed-consent-trial-participants-francois-houyez_en.pdf
- [7] Simplifying the process of seeking and recording consent in low risk clinical trials - Health Research Authority (accessed 2 June 2026) — https://www.hra.nhs.uk/about-us/news-updates/simplifying-process-seeking-and-recording-consent-low-risk-clinical-trials/
- [8] Patient in Clinical Trials - Information Folder, updated version 3.0 - Agencja Badań Medycznych (ABM) (accessed 2 June 2026) — https://abm.gov.pl/download/1/8525/Informationfolder-updatedversion30.pdf
