Want to know how long you are going to live? Try the longevity game at www.northwesternmutual.com/games/ longevity/index.html. Want to know if you are addicted to cocaine? Try www.sfvca.org/am_i_addicted_htm. Are you overweight? Go to www.netdoctor.co.uk/health_advice/facts/bodymassindex.htm.

If you know your blood pressure and blood cholesterol levels you can work out (with distressing accuracy) your chances of a heart attack or stroke within the next decade by using the calculator in BNF Extra (bnf.org/bnfextraframe.htm). It also, incidentally, contains a handy calculator for converting metric to imperial and back again.

If you want answers to those questions you never dared ask when you were a teenager about embarrassing things like sex, drugs and relationships, find the answers, entertain yourself and inform the kids at www.goaskalice.columbia.edu which is the University of Columbia's health education programme.

If all this stuff about health has made you want to crawl all around the human body, then www.nlm.nih.gov/research/visible/visible_gallery.html gives access to some of the pictures in the Visible Human Project database. Made up of Cat-scan and magnetic resonance imaging pictures, it shows you thousands of pictorial slices through the body of a convicted criminal, who donated his corpse to medical science.

Alternatively, you could try www.medtropolis.com/vbody, although the site was being rebuilt at the time of writing. If you are fired still further and want to practice being a surgeon, try synaptic.mvc.mcc.ac.uk/simulators.html. A University of Manchester site, it provides simulators to train doctors in everything from neurosurgery to heart catheterisation.

And if you are worried that trawling the web for health information may not merely turn you into a hypochondriac but prove addictive in its own right - it can. According to Kimberly Young, a US psychologist writing in the student version of the British Medical Journal, you are addicted if you answer yes to five or more of the following questions:

Are you preoccupied with the internet?

Do you need to run ever-longer sessions to gain satisfaction?

Do you stay on longer than you mean to, have you tried to cut back and failed, or have you ever lied to family members about your use of the net?

Has it jeopardised a relationship, or a job or educational opportunity?

And do you use the net to escape other problems, such as helplessness, guilt, anxiety or depression? (They may, of course, be the very reasons why you are trawling round the net in the first place!)

If you are addicted - don't worry. Help is at hand. Dr Young has her very own site (www.netaddiction.com) where, for a fee (naturally), you can be counselled out of your problem by e-mail, chatroom or television. Happy hunting.

Acknowledgements:
This guide could not have been compiled without the help of Robert Kiley at the Wellcome Trust, Bob Gann, Director of the Help for Help Trust and NHS Direct Online, Dr Jeremy Wyatt from the School of Public Policy at University College London, and staff at the Consumers' Association. The opinions and errors, however, remain all mine.