There’s a wealth of knowledge on medicine out there for people willing to look into it. While it’s not recommended that people literally become their own doctors, there’s plenty of information out there to educate yourself on medicine.
One of the most under-used resources is the military and military contractors. They produce field manuals, textbooks, and other resources, many of them for free, that can be downloaded and used.
FM-71 First Aid for the Soldier (PDF)
Military Medicine and Humanitarian Textbooks (covering all aspects of medicine, via the US Virtual Naval Hospital)
Brookside Press (huge number of textbooks, information, and videos on military medicine)