Everyone does it these days - as soon as we get a rash or a sniffle we go on Google to work out what's wrong.

But how does your doctor feel about you turning to the internet for a diagnosis before speaking to a real-life medical professional?

The answer: it can be good but it can also be disastrous, according to new research funded by Southern Cross Health Society.

Kantar researchers carried out 20 in-depth interviews with GPs across the country and 141 GPs filled out online surveys.

They found a growing trend of patients arriving at the doctor's office with firm views on what their treatment should be thanks to online research.

GPs worried about their charges using unreliable information sources, and were "shocked" at the lack of basic health knowledge among some patients, Southern Cross chief medical officer Dr Stephen Child said.

But Child said the internet was now most people's dominant source of information.

"We welcome patients being involved in their care and having conversations in that regard. So the internet and the additional information it provides can be of huge benefit to the doctor and the patient," he said.

"Some patients will try to self-diagnose and obviously can be extremely alarmed by what they see and think of the worst diagnosis," he said. "But people will also Google a treatment which doesn't have scientific support, and then [at the doctor] they will insist on being given garlic for their migraines.

"The diagnosis aspect is probably the greatest concern. For example if you Google 'aspirin side effects' you will find some scary results. But if you are given a course of aspirin at a low dose there are far more benefits than risks."

The media's tendency to republish the most dramatic medical findings could also skew what information people were exposed to online, Child said. The main problem is how to weed out the bad from the good information.

Southern Cross chief medical officer Dr Stephen Child said GPs surveyed were "shocked" at some patients' lack of basic health knowledge. Photo / Supplied

"Look at the conversations people have around vaccinations - that misinformation can be promulgated and do harm."

Misinformed patients also added to a GP's workload and took up valuable time that could be better used discussing actual care plans, Child said.

Patients accessing medical records through online portals could get anxious or misinterpret test results, posing another challenge for primary practice.

Medical professionals and the Ministry of Health have been working on the Choosing Wisely campaign, which aims to improve health literacy among patients and get them involved in their own healthcare.

Southern Cross sponsors the campaign and also has a online medical library, which offers medically-reviewed information.

Its research found while GPs had concerns about internet use, online communication, referral and booking systems were all considered valuable.

Ninety-one per cent of GPs texted patients to communicate, 88 per cent gave e-referrals to specialists and 53 per cent offered an online booking system.

But just 19 per cent were happy to give patients e-prescriptions, and GPs had mixed feelings about consulting via technology.

Consultation by phone was considered the most acceptable (at 53 per cent), while e-mail had low uptake at 32 per cent. Video consultation was least popular at 5 percent.

Food allergies the top mistake

People self-diagnosing with food allergies is the number one thing GPs see after patients pre-check their symptoms with Dr Google.

According to new research funded by Southern Cross Health Society there was a growing trend of patients arriving at the doctor's office with firm views on what their treatment should be thanks to online research.

Royal New Zealand College of General Practitioners medical director Richard Medlicott said patients that had researched their conditions could be well-informed, helping GPs make an accurate diagnosis.

"It can be a positive thing, general practitioners' can find out what the patient thinks and explore that and the patient may be right or wrong."

He preferred a patient that made an effort to understand what was wrong by using the internet than not at all.

But reading into symptoms could mean patients misdiagnosed themselves before they even stepped into the doctor's office.

"People often think they have a serious illness but it's often a busy life, too much alcohol, relationship problems or anxiety.

"Sometimes its vague symptoms like bloating, getting tired. That will get paired up with a wheat allergy."

Food allergies were the most commonly self-diagnosed illnesses - often without factual basis.

There had been cases of people sending hair samples overseas to get results for things like heavy metal poisoning then reading into results, he said.

"People get fixated on a test result."

He agreed some patients came in with firm views on what their treatment should be, but should listen to their doctor's advice.

Generally people googling their symptoms were safe because the first page of search results would likely be from credible source.

But page three or four on Google was where people could get sucked into a "wormhole".

There was a danger if patients simply left diagnosis at the keyboard and did not come in for a check.

Rectal bleeding was a common condition that could mean something relatively harmless or could be life-threatening.

If a patient self-diagnosed online with piles when it was actually cancer, it could be a deadly mistake.