A teenager who survived for nearly nine weeks in bushland in Sydney’s north was found covered in leeches and bites and had lost nearly half of his weight during his incredible ordeal, rescuers say.

Matthew Allen, 18, is also believed to be suffering from gangrene to his feet and lower legs and was suffering from partial blindness when he was discovered by hikers lying in the bush in Westleigh on Saturday afternoon.

Found ... Matthew Allen.

The teenager, an accountancy student who lived with his family less than two kilometres away in Westleigh, told his rescuers that he had survived only by drinking water from a creek bed that was almost dry.

He was not living under any shelter and was suffering from extreme exhaustion and dehydration when he was winched out of the bushland on Saturday afternoon.