A black labrador had to be rescued from the UK’s highest mountain after falling seriously ill when she ate cannabis, her owner has said.

Five-year-old Tokyo became unwell and even lost consciousness several hours into a hike up Scotland’s Ben Nevis last Sunday, according to her owner Christina Bluhme.

“She’d been so happy eating treats and drinking and had been her very active normal self,” Bluhme, a professional dog trainer, told CNN on Monday. The two had been trekking alongside Bluhme’s 17-year-old son Magnus and their two-year-old golden labrador, Blaze.

Then things took a dramatic turn as they approached the peak of the mountain, which stands at 4,413 feet (1,345 meters).

“We were maybe an hour from the top when we noticed Tokyo got really weak in her hind quarters,” said Bluhme.