OBJECTIVE Define the literacy level of Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HCMFUSP) outpatients, for the purpose of identifying recommendations to adapt writing of the informed consent form to the outpatients literacy level, since these can become the subject of research. METHODS Quantitative cross sectional study with 399 subjects. The sample was intentional, selected from different outpatient care units of HCFMUSP. Data collection used an instrument that contained a text with prose compatible for assessment of reading skills needed for comprehension of the consent form. RESULTS More than 46.6% of the interviewees were classified as functionally illiterate, of these, 12.7% were even unable to understand the proposed task in the text they read. Nevertheless, nearly 50% of the interviewees reported having at least started high school. CONCLUSIONS The results and the orientations for the text writing centered on the reader allowed us to make recommendations to render the consent form easier to read. We recommend that the researcher modifies the text to a structural narrative, addressed to the reader, using terms that are familiar. In other words, with terms common to the subjects' and to the medical language. In addition to improving the relationship between the subject and researcher, it is believed that these recommendations may reduce the time taken for the proceeding of research projects, since problems in the wording of consent forms contribute significantly to project delays.