The most popular sites in all 'Health' categories, according to the Alexa Toolbar. Updated daily.
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1.
US Government department in charge of medical research.
www.nih.gov
Site info for nih.gov 
2.
A health resources for consumers, physicians, nurses, and educators. Includes news, chat forums, health quizzes and consumer product updates.
www.webmd.com
Site info for webmd.com 
3.
Drug store chain. Features online buying facilities, career opportunities, company news, and investor information.
www.walgreens.com
Site info for walgreens.com 
4.
Medical dictionary, disease symptoms and treatments, resources for healthy living, and information on drugs and medicines.
health.yahoo.com
Site info for yahoo.com 
5.
Content designed, written, and developed by a woman physician covering topics such as menopause, breast cancer, pms and breast feeding.
www.focusonwomenshealth.com
Site info for medicinenet.com 
See top sites in all 'Health' categories