OTTAWA — is that tennis elbow or a tumour?

If you’re relying on the Internet to make the diagnosis, you may want to think again. Doctors warn that Internet self-diagnosis could have dangerous consequences.

Surveys show that most Canadian adults use the Internet to find health information, and doctors have noticed some trust it enough that they don’t even consult a physician.

“The power and the peril that we have right now, with particularly strong search engines, is you can input a string of symptoms and most assuredly something will pop out,” says Dr. Ross Upshur, a University of Toronto scientist and Canada Research Chair in primary-care research.

Search engines can give wacky advice. a Google search for “diet” turns up a fasting regime with lemon-concentrate pills exceeding Canada’s Food Guide. and the top results for “sore throat” suggest it’s a symptom of throat cancer or AIDS.

It turns into a problem when patients bring reams of papers to a doctor’s office explaining why their headaches are caused by meningitis. Doctors and international media call those web-stoked fears “cyberchondria.”

Upshur says he’s even more worried that some people don’t seek a doctor’s opinion after a Dr. Google diagnosis.

“I’ve got abundant anecdotal experience,” says Upshur, who meets with 50 to 60 patients each week. “For example, a patient with abdominal pain (who self-diagnosed) mild constipation … turned out to have gallstones.”

Upshur has seen patients who took medicines or tried treatments they find online before consulting him. Many buy so-called natural remedies, which often don’t help and aren’t thoroughly tested for side-effects.

He says their symptoms get worse as a result.

A Statistics Canada survey suggests 70 per cent of Canadian home-Internet users consulted the web for health information in 2009 — a jump from 59 per cent in 2007, overtaking news, sports and online banking.

An international report suggests 46 per cent of people who search for health information online do it to make a self-diagnosis. the report was published by U.K. health insurer Bupa in January, based on a study of 12,000 Internet users in 12 countries.

The same report warns that no sponsored website in the United Kingdom provides entirely accurate health information, though the country’s government websites all do.

The United States government struck a deal with Google last year to rank its own advice above that of drug companies when users do searches on pharmaceuticals.

Health Canada warns Canadians not to buy prescription drugs without a prescription and to consult a physician even when turning to alternative remedies. But search engines in Canada often put Wikipedia’s advice first, above that of government-sponsored information.

“The other trend I’m observing is not only self-diagnosis but self-treatment,” says Dr. Gunther Eysenbach in Toronto.

Eysenbach, editor-in-chief of the Journal of Internet Medicine Research, says YouTube is an unmonitored platform for amateur health advice.

Non-doctors upload videos that suggest anything from exercising away carpal tunnel syndrome to removing warts with liquid nitrogen or hot incense.

“In some instances, it’s nice that patients educate each other, but it’s probably also worth it for the medical profession to keep a watchful eye,” says Eysenbach. “Maybe doctors can help by commenting on this kind of video.”

The issue of web-browsing Canadians skipping doctor appointments is in Upshur’s and Eysenbach’s fields of research, but neither knows of any studies that address it.

“How often it happens is the bigger question that I don’t think anybody has an answer to,” says Upshur.