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.
"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.
"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 per cent.
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."