An Australasian clinical trial has shed light on the most efficient level of blood thinning treatment needed for patients hospitalised with COVID-19.

Patients in hospital with the virus are at increased risk of blood clots (or thromboses), which in turn may contribute to development of organ failure.

Almost all patients will receive some degree of blood thinning medication.

In an international study published in the New England Journal of Medicine - Evidence, researchers conducted a randomised clinical trial to test different levels of anti-coagulation (blood thinning) in more than 1500 patients in Australia, New Zealand, India and Nepal.

They found that a medium-level dose of the blood thinner was 86 per cent better in breaking down blood clots than any other type of dose.

Professor Steven Tong, an infectious diseases researcher at the Royal Melbourne Hospital, said the findings will inform World Health Organisation sponsored guidelines.

"Current practice in Australia is for low dose of anti-coagulation, while international guidelines recommend the high therapeutic dose of anti-coagulation," he explained.

"Our findings provide evidence that a middle ground may be most beneficial."

The George Institute for Global Health's Professor Bala Venkatesh said the study's comparative scope to include patients in the second most populous country in the world, India, was necessary.

"This study highlights the importance of conducting clinical trials in different health care systems," Prof Venkatesh said.

"Low and middle-income countries (LMIC) have been under-represented in COVID-19 studies and (this study) is one of the few studies to have a major involvement of LMIC regions."