There is a large overlap between medicine and biology, a lot of medical questions are in the end questions about human biology. Where do we want to draw the line on medical questions, when are they off-topic here?
In my mind, the line should probably be drawn between "What should I do?" and "How does this work?". Biology is the mechanistic explanation for most of medicine, so those questions should be on topic.
I think that any question asking for medical advice is very much off topic (and gets into a potentially ethically or legally dubious area).
I agree that many (most?) medical questions are human biology questions. But I would take it one step further: medicine is best understood using basic concepts of biology.
I think that, if marginal medicine questions are asked, we should work to reformat them as biology questions. In the end, this serves two purposes: (1) we have a better question base and (2) we can educate the public about biology and why they should care (i.e., their health).
I like this question: Why Does Salt Water Help Sore Throats?, which could have been posed as a medicine question, but really is more of a membrane biology/biophysics/microbiology question. Imagine the question as "Will gargling with salt water help my sore throat [see photo]?"