Couples and families may be missing out on medical rebates by not registering for the Medicare Safety Net, Human Services Minister Michael Keenan says.

Couples and families are being urged to register for the Medicare Safety Net or risk losing out on hundreds of dollars a year in medical rebates.

Individuals are automatically registered for the safety net but couples and families aren't.

"It is as simple as picking up the phone and calling Medicare, or you can even update your details online through our websites and apps," federal Human Services Minister Michael Keenan said in a statement on Monday.

When out of pocket medical expenses reach an annual threshold, the safety net provides a higher Medicare rebate each time Australians visit the doctor before the end of the calendar year.

For concession cardholders and families on family tax benefit part A, the threshold is $668.10.

The threshold is $2093.30 for other Medicare cardholders.

A safety net also applies for the Pharmaceutical Benefits Scheme.