After-hours home doctor services have begun shutting down as a result of recent Turnbull government cuts to Medicare rebates, sparking fears of further pressure on hospital emergency departments.

The National Home Doctor Service - the country's largest provider of home visits - has begun sending letters to patients in NSW, Queensland, Tasmania and Western Australia to tell them of imminent closures.

"As you can imagine, it is already difficult to get doctors to work in the after-hours period - especially given most of them choose to work during the day rather than drive long distances at night and often in inclement weather at personal risk," says one of the letters, obtained by Fairfax Media.

"This Medicare cut has made recruitment and retention of doctors close to impossible. We apologise for the inconvenience that this may cause and we take the opportunity to thank you for your support."

The first closures will occur in Perth, Hobart, Albury and Townsville in the coming weeks but more are expected.