No original research
"Original research" on Wikipedia means drawing any conclusions that are not specifically mentioned within a cited source. This is true of all articles, but is particularly crucial for medical content.
Never use material from different sources to suggest a conclusion that isn’t explicitly stated by those sources. If one reliable source says A, and another says B, resist the temptation to connect A and B in your article.
Pay close attention to your paraphrasing of medical information, and make sure that your content is accurate without citing the original text too closely.