Newly minted world record-breaker Kristin Harila is done with 8,000-metre mountains and ready for a "normal life" after achieving her goal of giving women a rare role model in extreme climbing.

The 37-year-old Norwegian and her Nepali guide Tenjin "Lama" Sherpa became the fastest people to summit the world's 14 highest mountains after reaching the top of mighty K2 in Pakistan's Himalayas on Thursday.

Together they completed the feat in three months and one day, surpassing Nepal-born British adventurer Nirmal Purja's record, set in 2019, of six months and six days.

"I haven't been thinking too much about the record... for me, I wanted to change something," Harila said about the male-dominated climbing sphere.

"If you go and look at history, it's been all about men. And I think that if it's going to change, we need to have some profiles and we need to take some place."

More than 40 people have summited the world's 14 "super peaks" that rise above 8,000 metres (26,250 feet), only a few of them women.

Harila, who had a custom-made down suit because none in the market fitted her slender female frame, hopes her success will help more women to secure attention and financial backing for mountain challenges.

- 'Very, very challenging' -

Harila spoke to AFP in Islamabad on Sunday evening, after waking up in K2 base camp the same morning and flying back part of the way by helicopter.

She was exhausted after completing a summit every 6.5 days for the past three months.

"It can be very, very challenging. And sometimes I'm just like, so tired. Like super tired, like I'm falling asleep," she said after enjoying her first shower in weeks.

"Sometimes you have really good days and just enjoying good weather and friends. And sometimes I'm really sick and throw up a lot and have a bad stomach."

Harila's rise to prominence has been rapid compared to other climbers at her level and, having started climbing in 2019, marked by dogged determination.

She gave up her job with a chain of furniture stores and sold her apartment to partly fund the expedition, for which she later secured some funding from brands including watch and backpack manufacturers.

She set out to achieve the record last year but suffered a crushing setback when Chinese visas for the last two mountains took months to come through.

The only route to the record was to repeat the ascent of 12 of the mountains.

"Of course, I was very disappointed last year when we didn't get the permit, but I decided immediately 'it's okay, I'm doing it again next year'. Of course, I have regretted it a little bit!" she joked.

Harsher weather conditions this year compounded the effort, with K2 blanketed with deep snow that, together with a bottleneck of climbers, almost tripled the final stage of the ascent from five hours to 14.

There was little time to celebrate at the top.

"When I realise that we are going to reach the summit, I cry a little bit... But we also knew that it was a very tough condition there this year, and we had to go down," she said, having been wary of avalanche risks and dwindling oxygen supplies.

- 'I'm finished' -

Harila was thrilled to share the record with Lama, who has been a guide since the age of 16, fearing that one of them would get sick or injured before the end of the challenge.

"When we met on the first mountain it wasn't planned at all. I didn't know him. He didn't speak much English, like a few words. And I speak a few words of Nepali, and yet we understood each other perfectly," she said.

"He was just amazing. We kept each other safe."

Now she intends to settle back in Norway, where she aims to call out sports firms on their poor record of sponsoring women athletes.

She'll also pick up running and take a slower approach to life.

"For me the hardest thing has been to be away so much from my family and like missing Christmas and birthdays. And all these holidays we had and my grandma died and I couldn't be there," she said.

"I'm going home to have a normal life, live with my boyfriend, then get kids, get married. I'm finished with 8,000 metres," she said.