Tens of thousands of specialist doctors are joining GPs' war against the Turnbull government's extended freeze on Medicare rebates, increasing pressure on the Coalition's health record ahead of the federal election.

The Australian Medical Association has distributed posters to its members, warning patients that they will be out of pocket because the cost of running the medical practice will continue to rise as Medicare rebates stay frozen until 2020.

AMA President Professor Brian Owler.

"You will pay a new or higher co-payment every time you visit your GP, every time you visit other medical specialists, every time you need a blood test, and every time you need an X-ray or other imaging," it says, alongside a photo of a woman comforting a crying child.

It comes a week after the Royal Australian College of General Practitioners announced its 32,000 members would urge their patients to lobby local MPs against the move. The groups share about 8000 members, adding about 22,000 more specialist doctors to the campaign.