Today there are literally thousands of medical websites online. But which are the best health care websites? Which can you trust? Needless to say, you should be extremely careful which Internet sites you rely on for vital health information and advice! Following are three proven, reliable health care megasites which, by common consent, are among the most reliable and trustworthy.

1. Mayo Clinic

"The Needs Of The Patients Come First" has been the primary and the underlying principal of this world-renowned nonprofit healthcare clinic established by the Mayo brothers in 1889 in Rochester Minnesota. The company's huge website, at mayoclinic.org, provides diagnostic and treatment information on virtually every disease and ailment known, all of which are listed alphabetically.

If you click on, say, Acute Leukemia, the link takes you to a page offering an overview of the disease, as well as a listing of the various blood tests and other diagnostic methods available. The patient can then read details about treatment options which are available. One especially nice feature of the site is that it offers stories of real people who have won the battle against serious illnesses such as acute leukemia.

Additional features include complete profiles of the various doctors who are serving at the Mayo Clinic and the capability to make online appointments with them. You can also refill prescriptions and view and pay bills on the site.

2. WebMD

Webmd.com is an amazing source of online medical information. True to its punch line, "Better Information, Better Health", this website has a lot to offer. For starters, it can be used to locate a specialist or a hospital close to your home location. If you are planning to take a drug that is new to the market, then you definitely need to visit the review section to find details about it before starting to use it.

On the WebMD home page you can find a number of attractive slide show packages dealing with topics varying from how to increase the chances of pregnancy, to a recommended thirty minute workout schedule, to a slide show on dental fixes. There are lots of medical news tidbits as well as an Expert column that enables you to send a query to an expert. You can even post your own tips and advice on the message board. If you are overweight and planning a diet, then use the BMI calculator to find your ideal body weight and a calorie calculator to find how many calories you burn during half an hour walking expedition. The site has many other diagnostic features and services ? too many to list here. Overall, it's terrific place to begin most kinds of online medical research. In fact, you may not need to look any further.

3. Revolution Health

Revolution Health (revolutionhealth.com) is an amazingly comprehensive health information website. Take a few minutes to look it over - it's a resource you should probably bookmark. Registration is required but this merely requires that you provide your email address and set up a password. For this small investment in time you will have access to doctor-finding and rating tools, hospital comparative rating charts, disease/medication/treatment research tools, health risk assessment, exercise tracking tools, a 6-week healthy living program, many free newsletters, and much more. You can also sign up for a Premium Membership which provides a "Health Assistant and Advocate" to counsel you in dealing with virtually any type of health question or concern, from finding treatment options to dealing with your health insurance provider. It's a very cool, very useful site and you could spend many hours profitably perusing it.