Faced with unaffordable student loan repayments, many UK graduates on moderate salaries are leaving their jobs, or turning down promotions in sectors plagued by staff shortages, such as teaching and healthcare. Loans totalling as much as £120,000 – many swollen by surging interest rates – are putting them off trying to progress in their careers, people responding to an online callout or explaining their experience in interviews shared with the Observer.

The repayments also made buying a home much harder or impossible, they said, and were affecting their mental health and plans to start a family.

Many said they had avoided jobs with salaries high enough to trigger student loan repayments, with some opting to work in part-time minimum wage jobs despite having degrees in sought-after subjects. Several said they had left or not applied for jobs paying more money because of the resulting higher loan repayments, and having to pay the 40% income tax rate.

Olivia, a 30-year-old project manager whose £68,000 debt when she graduated has grown to nearly £75,000, said she took a lower-paid role to decrease the monthly repayments of £350, which she struggled to afford. “Combined with the lower tax rate and lower repayments, I am actually better off financially,” she said.

Lucy, from Shenfield, Essex – who was the first in her family to go to university, gaining a maths degree in 2007 – worked briefly in graduate roles as a transport planner and in private equity. But on an annual salary of £20,000, she felt her student debt was hanging over her. She moved back to her parents’ house and has been in part-time minimum-wage jobs since she was 25. For the past six years, she has been a taxi controller, earning £19,000 last year.

“My student debt makes me not want to earn more, as my equivalent rate of tax would be 38%,” she said. “I see not repaying my loan as an act of defiance.”

NHS dietitian Carrie, from Cheshire, was one of several people who said they were borrowing to clear their student debt. Owing about £20,000, Carrie has been making repayments, currently about £300 a month, since 2019. “I’d assumed the debt was coming down but I’ve discovered I’m barely covering the interest,” she said. “As my payments will go up with any pay rise I get, I’ve decided to pay off my loans with [a] remortgage.”

Carrie works 37.5 hours a week in her main job and has taken a second job for 7.5 hours, as different jobs are assessed separately for student loan repayments. She will now not be mortgage-free until she is 73. “It seems drastic,” she said, “but it makes sense to escape this tax that I’d pay forever otherwise.”

Several below-average and middle-earners felt leaving their chosen careers for higher-paying sectors such as IT, banking or business was the only way forward.

However, Buckinghamshire teacher Kevin took out a £27,000 student loan three years ago to do a part-time master’s in education management, hoping to get into better-paid school management.

“The master’s was a waste of time and money, as it turns out schools do not value it,” he said, adding that the “mercilessly high” repayments were unaffordable on his teaching salary. Having retrained as a data protection officer, Kevin is hoping to find a new job by Christmas.

Another teacher from the south of England said the UK student loan system was “clearly disincentivising joining the teaching profession”.

Although some people – such as doctors and lawyers – acknowledged that they needed a degree in their field and would probably earn less in a non-graduate role, many felt trapped by having to repay loans from stagnating graduate wages, which have been losing buying power since the cost of living crisis over the past few years.

“I don’t think I’d have had the same opportunities without my degree, but it’s hard to say,” said Daniel, 27, a software engineer from Norwich. “My take-home pay is £3,400 a month, but I still owe about £70,000, and that has increased substantially since I graduated in 2019.”

He thinks he will probably never pay off his loan, and views his monthly repayments of £220 as a “frustrating tax the new Labour government will hopefully be looking at,” adding: “Any sort of relief for those repaying student loans would be good.”

Several respondents who had qualified in lower-paid fields, such as nursing, paramedics, teaching, the civil service or the arts, said they regretted their degree and felt “trapped” and “misled” by those who had advised them to take out a student loan. The majority also said they had not fully understood the terms of their loans when they took them out.

Carmen*, 43, a doctor from Aylesbury who has been repaying her loan since 2015 and still owes £36,000, said she was advising younger family members to skip university: “I would be better off if I hadn’t gone to uni. My sister, who has [significantly fewer] qualifications, and is admittedly paid less than me, has more free cash.”

Mazaher Muraj, 35, a software engineer from Milton Keynes, graduated in 2011 owing £18,000 and is repaying about £350 a month. “My first graduate job paid £20k,” he said. “I’m now on nearly £70k, but, knowing what I know now, I don’t think university was worth it. Only a fraction of my colleagues have degrees; many are self-taught or have done shorter courses.”

He said he had to consider the effect of higher student loan repayments triggered by every salary increase offer on other financial commitments he has.

*Name has been changed