Accessibility is one of six quality criteria articulated by the European Commission in its code of conduct for health websites. Readability plays an integral part in determining a website's accessibility. Health information that is hard to read may remain inaccessible to people with low health literacy. This study aimed to calculate the readability of websites on various causes of disease. The names of 22 health conditions were entered into five search engines, and the readability of the first 10 results for each search were evaluated using Gunning FOG, SMOG, Flesch-Kincaid and Flesch Reading Ease tests (n=352). Readability was stratified and assessed by search term, search term complexity, top-level domain and paragraph position. The mean reading grade was 12.30, and the mean FRE was 46.08, scores considered 'difficult'. Websites on certain topics were found to be even harder to read than average. Where conditions had multiple names, searching for the simplest one led to the most readable results. Websites with .gov and .nhs TLDs were the most readable while .edu sites were the least. Within texts, a trend of increasing difficulty was found with concluding paragraphs being the hardest to read. It was also found that some of the most frequent search results (such as Wikipedia pages) were amongst the hardest to read. Health professionals, with the help of public and specialised libraries, need to create and direct patients towards high-quality, plain language health information in multiple languages.