For basic information on health issues, you may use a variety of library and online sources--think about this as using reference sources for gathering information.
Here's a variety of resources from the library--some books (the "sourcebook" series, which are paper books) and some reference database sources.
The library has many reference books with health information. Here's a couple of examples.
Here are some good quality web resources for health information.
Also consider websites for advocacy or medical association groups, which often have good information about health issues. Here's a couple of examples--