A local doctor went for a walk. Three months later she's been reported missing

A woman who told her family she was going on a walk has been reported missing three months later in Western Australia.

Police hold concerns for Casal as she was only reported missing last week. Source: AAP / WA Police

A woman who vanished after reportedly telling family she was going for a walk has been reported missing, three months after she disappeared in Western Australia.

Nathalie Casal told family she was going to walk the Bibblumun Track, about 30km east of Perth, with "a large group" in December last year.

The 71-year-old hasn't been seen since.

"Dr Casal advised family in December that she was going to walk the Bibblumun Track with a large group and may not be reachable for some time," WA Police said in a statement on Thursday.

Police believe she may have started her walk from Mundaring, a popular launching point for many of the trails in the area.

Casal is described as being approximately 157cm tall with a slim build, short grey hair and brown eyes. Source: AAP / WA Police

Casal's family said her disappearance was out of character and reported her missing on March 7.

She is described as being approximately 157cm tall with a slim build, short grey hair and brown eyes.

Concerned locals responded to the WA Police's missing person's report on its Facebook page on Thursday afternoon.

Many said she is a much-loved GP in the area.

"She was my GP for 15 years," one comment said. "I hope she is found well and safe."

The Bibbulmun Track is a long distance 1000km trail running from Kalamunda in the east of Perth to Albany.