Doctors are concerned that increasing numbers of people are using the internet for self-diagnosis.
Almost four out of five Southern Cross customers surveyed said they had used the internet for medical matters. The figure is up 7% from two years ago.
Of the 566 Southern Cross members surveyed, nearly 40% said they would challenge a medical professional's advice on the basis of their own internet research.
Medical Association chairman Peter Foley says patients should be wary of misinformation and they should be told of the importance of seeking professional advice for health problems.
However, Dr Foley says says it is understandable that people will seek additional information and doctors often direct patients to reputable internet sites.