National Institutes of Health is part of the U.S. Health and Human Services Department. The site contains information on various diseases and disorders, hotline number to call with questions, tips on making doctor visits more useful, and links to specific institutes, such as the National Eye Institute or the National Cancer Institute.

https://www.nih.gov/

Some find Medline Plus, the NIH’s National Library of Medicine site, to be more user friendly. In addition to health topics and diseases, it offers a guide to drugs and supplements. Helpful videos are included.

https://medlineplus.gov/

Healthfinder.gov is another Health and Human Services site with general information, primarily geared to preventing diseases and maintaining a healthy lifestyle.

https://healthfinder.gov/

The Mayo Clinic is known internationally for its research as well as its patient care. Their website includes general health information, symptoms and treatments for specific diseases, and current research on various conditions, including clinical trials.

http://www.mayoclinic.org/

Also, drug store chains such as Walgreens, CVS, etc. often have a pharmaceutical section at their website with information about various prescription drugs including side effects and uses.