The UK's medical profession is at a "crunch point", facing the prospect of too few doctors to treat rising numbers of patients, the regulator says.
The General Medical Council says the supply of medics has failed to keep up with demand and warns against the over-reliance on overseas staff post-Brexit.
The GMC's Charlie Massey called it a "crucial moment" for UK healthcare.
It comes despite government promises in England to increase the number of doctors in training.
The annual report by the GMC highlights four areas of concern:
- Supply of new doctors into the UK has not kept up with demand
- A dependence on non-UK qualified doctors in some specialist areas
- The risk of some overseas doctors being put off working in the UK after Brexit
- An ongoing strain on doctors in training
If you can't see the NHS Tracker, click or tap here.
The report found the number of doctors on the medical register had grown by 2% since 2012, at a time when there has been a 27% increase in A&E attendances in England and a 10% increase in Northern Ireland.
Moreover, the growth in the population of those aged 85 and over - often the most needy in medical terms - is projected to double from 1.6 million to 3.2 million by 2041.
"The medical profession will undoubtedly need to grow to meet this extra demand," the report found, adding that it must equally consider in which areas, medically and geographically, that growth should be focused - highlighting rural locations where recruitment remains a challenge.
Mr Massey called on the UK government to "think carefully about how many doctors are needed, what expertise we need them to have so they can work as flexibly as possible, and where they should be located given the changes and movement in population expected".
In addition, the number of licensed doctors who are non-UK graduates has reached 43% in areas such as the east of England, 41% in the West Midlands and 38% in the East Midlands.
Some specialist areas are particularly reliant on doctors recruited from overseas. For example, more than half the workforce in obstetrics and gynaecology are currently non-UK graduates.
While acknowledging the importance of pooling knowledge and experience with other countries, the report questions whether "our reliance... should be reduced in favour of a more strategic and sustainable approach".
The impact of Brexit too remains a concern.
In 2017, there were 6,000 fewer non-UK graduates on the register than in 2011.
South Asia accounts for nearly half the fall, but surveys taken earlier this year suggest European doctors currently working in the UK are also considering their position, in the light of the UK's decision to leave the European Union.
"The underlying challenge for all in healthcare is how we retain the good doctors we have right now," said the GMC's Mr Massey.
"Everything we hear from the profession tells us that we need to value them more."
He stressed the need to help doctors "achieve the right balance between their professional and personal lives through more flexible working arrangements".
Lack of sleep
In the wake of last year's junior doctors' strikes and countless media reports, it is clear doctors are unhappy with their lot.
Both those in training and those doing the training complain of their heavy workload, and subsequent lack of sleep.
It has become common for more than half of doctors to take a break after completing foundation training - some do not return.
You might also like:
To meet the future needs of patients, the GMC stressed the need to reduce the burden on doctors through better training and more flexible working conditions.
"The pressure on our health services shows no signs of letting up," said Mr Massey.
"It's on all of us to understand why doctors are making different choices about their lives and careers."
Labour shadow health secretary Jonathan Ashworth said: "Tory mismanagement of the NHS workforce has been a disaster for staff and patients alike."
But the Department of Health in England said there were record numbers of doctors working in the NHS - up by nearly 15,000 since May 2010.
A spokeswoman also pointed out that the number of training places was increasing by 25% in the coming years.
"We are also making sure we retain those already working in the NHS by improving doctors' work-life balance and supporting flexible working," she added.