A YOUNG British backpacker, found alive after three nights lost in the Queensland outback, survived by drinking contact lens fluid and his own urine, his mother says.

Claire Derry said her 18-year-old son Sam Derry-Woodhead lost 15 kilograms during his ordeal in searing heat on a remote property 130 kilometres from Longreach.

Rescue .. a joyful Claire Derry before flying to Longreach to see her son. Credit:Michel O'Sullivan

He tried drinking his urine but that didn't go well. So he drank tiny sips of the contact lens fluid he had with him.

The teenager, who went missing on Tuesday afternoon from Upshot Station where he had spent about 10 days working as a jackaroo as part of his gap year, was found sunburnt and dehydrated on Friday.