Objectives Patient information sheets (PISs) and informed consent forms (ICFs) are essential tools to communicate and document informed consent for clinical trial participation. These documents need to be easily understandable, especially when used to take informed consent from acutely unwell patients. Health literacy guidance recommends written information should be at a level between reading ages 9–11. We aimed to assess the readability and complexity of PISs/ICFs used for clinical trials of acute therapies during the COVID-19 pandemic.

Design Retrospective document analysis.

Setting PISs/ICFs used in trials involving pharmaceutical interventions recruiting hospitalised patients with COVID-19 during the first year of the pandemic were sourced from hospitals across the UK.

Primary and secondary outcome measures PISs/ICFs were assessed for length, approximate reading time and subsection content. Readability and language complexity were assessed using Flesch-Kincaid Grade Level (FKGL) (range 1–18; higher is more complex), Gunning-Fog (GFOG) (range 1–20; higher is more complex) and Flesch Reading Ease Score (FRES) (range 0–100; below 60 is ‘difficult’ for comprehension).

Results 13 documents were analysed with a median length of 5139 words (range 1559–7026), equating to a median reading time of 21.4 min (range 6.5–29.3 min) at 240 words per minute. Median FKGL was 9.8 (9.1–10.8), GFOG 11.8 (10.4–13) and FRES was 54.6 (47.0–58.3). All documents were classified as ‘difficult’ for comprehension and had a reading age of 14 years old or higher.

Conclusions All PISs/ICFs analysed contained literary complexity beyond both recommendations and the reading level of many in the UK population. Researchers should seek to improve communications to improve trial volunteer comprehension and recruitment.