Key takeaways
- Article 26 of EU Clinical Trials Regulation 536/2014 lets each Member State decide the language of the application dossier, while encouraging a commonly understood medical language for documents not addressed to participants.
- Article 29 of the Regulation requires information for informed consent to be comprehensive, concise, clear, relevant and understandable to a layperson.
- Article 69 leaves the language of investigational medicinal product labels to the Member State concerned and allows multilingual labels.
- Sponsors must submit a summary of results with a version for laypersons to the EU database within one year of the end of the trial in all Member States concerned.
- New UK clinical trials regulations came into force on 28 April 2026 and require a summary of results to be published within 12 months of trial completion.
This guide is for sponsors, contract research organisations (CROs) and study managers running multinational trials. It explains which clinical trial documents usually need translation, what EU and UK rules say about language, and how to organise translation so it does not hold up submission or recruitment.
The focus is on documents rather than people: interpreting during consent visits is a separate service, discussed in our article on working with interpreters in healthcare settings.
Which clinical trial documents need translating?
Clinical trial documents need translating when the person who must read them, whether a regulator, ethics committee member, investigator or participant, does not work in the source language. The audience determines both the language and the register of each translation.
| Document | Main reader | Translation consideration |
|---|---|---|
| Protocol and investigator's brochure | Regulators, ethics committees, investigators | Often accepted in a commonly understood medical language; check national rules |
| Participant information sheet and informed consent form | Participants and their representatives | Must be in a language the participant understands and written for a layperson |
| Patient diaries and questionnaires | Participants | Outcome measures need linguistic validation, not only translation |
| Investigational medicinal product labels | Site staff and participants | Language set by each Member State; multilingual labels allowed |
| Recruitment material and lay summaries of results | Public and participants | Plain language, culturally appropriate wording |
| Safety reports and source documents | Sponsor safety team and regulators | Fast turnaround and exact medical terminology |
What does the EU Clinical Trials Regulation say about language?
The EU Clinical Trials Regulation (CTR), Regulation (EU) No 536/2014, leaves most language decisions to each Member State concerned. Article 26 sets the rule for the application dossier:
"The language of the application dossier, or parts thereof, shall be determined by the Member State concerned. Member States, in applying the first paragraph, shall consider accepting, for the documentation not addressed to the subject, a commonly understood language in the medical field." (Regulation (EU) No 536/2014, Article 26)
In practice, technical documents such as the protocol may be accepted in English where a Member State chooses to accept a commonly understood medical language, while documents a participant reads need the participant's language. Each sponsor needs a country-by-country list, because the Regulation itself does not fix one.
Article 69 applies the same approach to labelling of investigational medicinal products (IMPs), the medicines being tested: "The language of the information on the label shall be determined by the Member State concerned. The medicinal product may be labelled in several languages." This allows one multilingual label to serve several countries in the same trial.
How should informed consent forms be translated?
An informed consent form must be translated so that the participant fully understands the trial, not just so that the words match. Article 29(2) of the CTR requires consent information to be "comprehensive, concise, clear, relevant, and understandable to a layperson".
The same article requires the information to cover the nature, objectives, benefits, risks and inconveniences of the trial, the participant's right to withdraw at any time, and possible treatment alternatives. Every one of those points has to survive translation with its meaning intact. A softened risk statement or a vague withdrawal clause can undermine the validity of consent.
What ethics committees may ask for
Some ethics committees and institutional review boards ask for evidence of how a consent form was translated. For example, the Duke University Health System policy on translation requirements for research requires review of the translation process "by either certified translation OR forward and back translation by two different people". Our article on back translation explains what that method can and cannot show.
What are lay summaries and when are they due?
A lay summary is a plain-language account of a trial's results written for participants and the public. Under Article 37(4) of the CTR, the sponsor must submit a summary of results to the EU database within one year of the end of the trial in all Member States concerned, "accompanied by a summary written in a manner that is understandable to laypersons".
Lay summaries are often translated into the languages of every country where participants were recruited. They need translators who can write simply without changing the findings, for example without turning "no statistically significant difference" into "the medicine did not work".
What do UK sponsors need to know?
UK trials now follow updated legislation. According to the Health Research Authority, the Medicines for Human Use (Clinical Trials) (Amendment) Regulations came into force on 28 April 2026, after a 12-month implementation period.
The HRA summary says sponsors must "publish a summary of trial results within 12 months of completion" and offer to share a summary with participants "in a way they can easily understand". For UK participants who do not read English well, that can mean translated participant information and translated result summaries.
How to manage translation in a multinational trial
- Map languages early. List every country, site language and participant population, including minority languages at individual sites.
- Write translatable source documents. Short sentences and defined terms reduce cost and ambiguity in every language.
- Build a study glossary for the investigational product, procedures, visit names and adverse event terms.
- Separate document types. Route outcome questionnaires to linguistic validation and consent forms to translation with independent review.
- Plan for amendments. Protocol amendments trigger updated consent forms in every language, so keep translation memories and version control.
- Prepare for safety reporting. Agree how site-level adverse event documents will be translated quickly; see our guide to pharmacovigilance translation.
Common mistakes in clinical trial translation
- Translating outcome questionnaires like ordinary text. Without cognitive testing, results from different countries may not be comparable.
- Losing version control. A site using an outdated consent form translation is a serious compliance finding.
- Over-technical consent language. Terms such as "randomised" or "placebo" need plain explanations in every language.
- Assuming one Spanish or French works everywhere. Participants in different countries may need local adaptation.
- Starting translation after approval of the English version without a buffer. Allow time for review and ethics committee comments in each country.
Clinical research is one strand of a wider field. For an overview of devices, medicines and safety translation, see our medical and pharmaceutical translation guide.
How TranslationWorks can help with clinical trial translation
TranslationWorks is a UK-based translation agency that translates clinical trial documents, including protocols, participant information sheets, consent forms, labels and lay summaries, using native-speaking professional linguists in more than 150 languages. Our medical and pharmaceutical translation team works remotely with sponsors and CROs, with human translation and independent review.
TranslationWorks is registered to ISO 17100, ISO 9001 and ISO 27001 and certified under Cyber Essentials, which supports the confidential handling of unpublished study data. Send us your document list, countries and timelines, and get a free quote for your trial translation within 24 hours.
