It was not immediately clear how many would heed the call, but on Monday some of the 15,000 doctors and interns at large hospitals tendered their resignations en masse, despite a government order for them to stay at work.
Ahead of the planned industrial action, major hospitals said they were adjusting surgery schedules and patient appointments.
Prime Minister Han Duck-soo had pleaded with doctors not to take "the lives and health of the people hostage". He also ordered emergency measures such as using telemedicine, expanding operations at public hospitals and opening up military clinics.
"It is most important to minimise public inconvenience caused by a vacuum in medical care, and in particular, it must never lead to a situation where critically ill emergency patients are at risk," Han told a meeting on Monday.
The government plans to boost medical school admissions by 2,000 starting in the 2025 academic year, with a goal of adding 10,000 doctors by 2035. The current annual student intake is about 3,000.
With a population of 52 million, South Korea had 2.6 doctors per 1,000 people as of 2022, far below an average of 3.7 for countries in the Organisation for Economic Co-operation and Development (OECD).
A Gallup Korea poll released last week showed around 76% of South Koreans support the plan, amid concerns about an acute shortage of doctors for paediatrics, emergency units and clinics outside the greater Seoul area.
But doctors and medical student groups have argued there are already sufficient physicians and that increasing the number would prompt unnecessary medical care and undermine the finances of the national health insurance plan.
They have also criticised the government for failing to consult and for "demonising" existing doctors.
Park Dan, head of the Korea Interns and Residents Association, said on Facebook that he had submitted his resignation on Monday because of what he called the government's "messy policy".
