There are calls for greater transparency around the charges specialist doctors set with data showing some patients are paying five times more than others.

Some Australians are paying five times more than others to see a specialist depending on their need and location, according to new research.

Analysis of Medicare claims published in the Medical Journal of Australia found certain states had higher bulk billing rates and that fees varied by an average of over 70 per cent.

In the field of neurology, the difference between the lowest and highest out of pocket expenses was approximately $189.

The research has led to calls for greater transparency in setting specialist charges.

Professor Gary Freed, of the Centre for Health Policy at the University of Melbourne, and Amy Allen, Melbourne School of Population and Global Health, analysed Medicare claims data from 2015 for an initial outpatient appointment with a consultant physician in eleven frequently used non-surgical specialties.

These included cardiology, endocrinology, gastroenterology, geriatric medicine, haematology, immunology/allergy, medical oncology, nephrology, neurology, respiratory medicine, and rheumatology.

Most visits required a significant out of pocket payment, with specialties bulk-billing on average between 30 to 42 per cent of visits.

The highest rates of bulk-billing were in haematology (60 per cent) and medical oncology (53 per cent), and the lowest in geriatric medicine (17 per cent).

Large differences were also seen between the different states and territories.

Doctors in the Northern Territory bulk-billed 76 per cent of visits, a greater proportion than anywhere else.

Bulk-billing rates in NSW and South Australia were just above 40 per cent, while Western Australia was the only state with a rate below 20 per cent.

Currently, the authors suggest, there is no way for patients to know if paying more means better care.

"As there is no publicly available information about the quality of care in the outpatient setting or any validated outpatient quality measures available in Australia, these fee variations are not based on any objective information about the care provided by individual doctors," they wrote.

The Royal Australasian College of Physicians (RACP) says doctors set fees based on a range of factors including the "complexity of care" and the costs of running a practice.

In recent years, the rebates provided through the Medical Benefits Scheme "have not kept pace with the costs of running a quality medical practice", an RACP spokesperson said in a statement to AAP on Monday.

"This has been exacerbated by the rebate freeze," they said.

The report authors say the policy of prohibiting insurance coverage for outpatient care may need to be reconsidered in light of the new data.