Doctors believe the Turnbull government could be contemplating another increase in the Medicare levy.

The Australian Medical Association has used its pre-budget submission to plead with the government to return any extra revenue raised by the tax to health rather than using it to fix the deepening deficit.

"It is equally important to understand that any increase in the Medicare Levy does not absolve governments from the critical need to continue to reinvest in Australia's health, including lifting the MBS freeze," the peak group says in its submission to the government ahead of the May 9 budget.

"It must not change the need for states and territories to continue investing in public hospitals, nor should it impact on the value case and viability for private health insurance," the AMA says.

A 0.5 per cent increase to the levy could deliver the government more than $4 billion in extra revenue a year.