This story was produced by our colleagues at the BBC.

Thousands of doctors in the United Kingdom who work for the National Health Service are going on strike — again — starting Saturday in a dispute with the government over pay. In the last few years, health professionals have been increasingly unhappy about their wages and conditions with the NHS. That’s led many doctors to leave the U.K. for the United States, Canada and other countries.

The National Health Service is famous around the world for being free of charge at the point of delivery. It’s funded through general taxation, and, although you can pay to be treated privately, most Brits still rely on and value the NHS, including U.S.-born actor Rob Delaney, who lives in London. He’s been supporting the doctors strikes.

“I love the NHS, and I love its workers, and my family’s benefited massively from it,” Delaney said. “Most of my life was spent getting health care in the United States, with a really horrible barrier of private health insurance in between me and my family’s care.”

Many British doctors are angry that they’re being made to work long hours for what they call inadequate pay. Dr. Kirsten Sellick, a striking medical resident, explained.

“I wasn’t earning enough to start paying off my student loan. I didn’t reach the minimum threshold to pay off my student loan,” she said. “And that’s how little I earned as a 40-hour-a-week doctor, which is part-time.”

The more years of training you complete, the higher your wages go. But even when you’re at consultant or attending level, you’ll still only earn an average of $180,000 a year. That’s far less than in the United States — in some cases under half the pay of equivalent U.S. doctors.

Dr. Shirin Ahmed is from the U.K. but now lives and works in America. On her YouTube channel, Ahmed talks about the salary differences.

“In the U.S., the average length of a residency program is around three to five years. Whereas in the U.K., when you finish medical school, the average length of training for a junior doctor is between five to 10 years,” she said.

Ahmed noted that consultants make two or three times less than they would in the U.S. 

But the U.K. government has said NHS doctors aren’t being reasonable. In the U.K., taxpayers pay doctors’ wages, and the government has pointed out that medical residents have already received an average 9% pay boost this financial year. It’s now offering them a further 3%.

The doctors aren’t happy, and some are turning their sights to Canada. That country has a similar free-to-all health system, publicly funded by the federal government and partly by each province.

Phil Martin, who’s based in the Canadian province of British Columbia, is the CEO of Physicians for You, which recruits doctors from abroad. He said he’s never been busier, and the route into Canada has never been easier.

“You can now actually get your full license without actually even getting into the country, which you never could before,” he said. “You’d have to sit multiple exams to do that. Also, they’ve removed supervision in some of the provinces as well, which sort of limited doctors where they could work.”

One doctor Martin has helped is family physician Dr. Ali Bryce, who also works in British Columbia. He said that, in addition to better pay than the NHS offered and less pressure, he wanted a different lifestyle.

“We wanted to go somewhere where we could enjoy the hobbies that we enjoy,” he said. “And Canada had a lot of that, with snow sports and outdoor hiking and just space, really.”

A recent survey by the doctors union, the British Medical Association, suggests 4 in 10 doctors are planning to leave the NHS and work abroad. The U.K. government says money is tight for increasing the salaries of British doctors — but it may have to find more cash or risk an even greater exodus abroad.