An international group of leading doctors and academics say up to one-third of many medical procedures are now being done unnecessarily, causing physical, psychological and financial harm that could threaten the viability of healthcare systems.

A landmark report in The Lancet medical journal said more needed to be done to address inappropriate medicine, which includes deliberate over-servicing by doctors for their own financial gain.

The researchers said about one in five knee replacements done after an arthroscopy to examine the joint in Australia were unnecessary, and that up to 70 per cent of operations to remove a woman's uterus (hysterectomy) in the US were inappropriate.

They also highlighted excessive use of allergy tests, vitamin D tests, colonoscopies, mammograms, MRI scans for lower back pain, and ultrasound screening for thyroid cancer.

In South Korea, the researchers said 99 per cent of a common type of thyroid cancer was now thought to be overdiagnosed, meaning it was never going to cause harm. Despite this, many people are being screened and having these cancers surgically removed, giving them a 2 per cent risk of vocal cord paralysis.

Over-use of medicine, which paradoxically exists alongside under-use of evidence-based medicine, is driven by defensiveness among health professionals who fear being sued; gaps in knowledge; erroneous beliefs; and lack of meaningful consultation with patients to understand their individual aims and preferences, the researchers said.

For example, some elderly people will not want a surgical investigation of a lump that could be cancerous when they're likely to die within a few years.

Other doctors may not have kept up with research showing that glucosamine for osteoarthritis of the knee offers little benefit to most patients, and some might be so frightened of missing a bacterial infection in a child that they prescribe antibiotics for viral infections such as coughs and colds that do not respond to antibiotics.

One of the researchers, Professor Paul Glasziou​ of Bond University in Queensland, said while there was a "fairly small" group of doctors in Australia who knowingly over-service, most want to do the right thing by their patients.

However, he said many well-intentioned health professionals were likely influenced by widening definitions of diseases driven by companies seeking to profit.

This applied to conditions such as "pre-diabetes" and new thresholds for high cholesterol, the latter of which has led to a growing proportion of people being prescribed lipid-lowering drugs with unclear benefits.

A new definition of chronic kidney disease has also led to large numbers of older people without symptoms being diagnosed, even though their urine shows no evidence of kidney damage.

The Lancet report said a fee-for-service payment system was likely fuelling the over-use of medicine in some countries.

"Physicians routinely act in conformity with their financial interests. Under fee-for-service payment, many specialties deliver higher volumes of services, distorted referral rates, and lower prevention activity than with fixed payment schemes, such as, capitation and salary," the researchers wrote.

The group said unnecessary medicine was expensive and likely to be undermining the sustainability of healthcare, with estimates it cost the US $210 billion in 2010.

Professor Glasziou​ said there was widespread recognition of the complex problem in Australia, and that many medical groups were working to reduce over-testing, over-diagnosis and over-treatment of people who could be harmed by medicine.

He said the federal government's review of Medicare was also looking at low value services to see if they still deserved taxpayer funding.

The part-time GP said some doctors might not be having detailed discussions with patients about the specific benefits and harms of tests and treatments, and what would happen if they chose to do nothing. He urged patients to prompt them so they know their options.

Researchers from the Lown Institute, University of Sydney, and Institute for Healthcare Improvement in the US, contributed to the Lancet series published on Monday.