Theresa May has hailed the dedication of NHS staff and said she is aware that health service staffing levels can leave them "frustrated", as she marked its 70th anniversary.
The Prime Minister cited the recent relaxation of foreign worker rules designed to ease pressure on medical staff as she hosted NHS workers at a Downing Street reception.
She told them the organisation was "a great British achievement" but needed to undergo changes to deal with new problems linked to an ageing population and childhood obesity, plus greater focus on mental health.
Mrs May addressed the cap on foreign doctors while talking about plans announced last month for a five-year funding deal which means it will receive an additional £20 billion a year in real-terms funding by 2024.
Discussing a 10-year plan to be drawn up by health service chiefs on how to best use the extra funding, the Prime Minister said: "I know that your dedication to your work is total.
"But I also know that, sometimes, you can be frustrated by staff shortages, and that you rarely enjoy the flexibility or work/life balance that many people now take for granted.
"We have already removed the cap on the number of foreign doctors and nurses who can come here each year, to relieve some of the immediate pressure on staff numbers.
"The plan will go further, investing in the workforce and introducing modern working practices so that the NHS is not just one of the biggest employers in the world, but also one of the best - managed in a way that works for patients and staff alike."
Last month Home Secretary Sajid Javid announced that the limit on so-called "Tier 2" visas for skilled workers from non-EU countries, imposed by Theresa May when she was in his role, was to be relaxed.
The visa limit has been set at 20,700 a year since 2011, with around 40% of places accounted for by the NHS.
In Wednesday's speech, Mrs May said there were "not many ideas from 70 years ago that are unquestionably supported today", but the health service was one of them.
She also used the speech to push for change within the health service to help it come with new problems linked to an ageing population and childhood obesity, plus greater focus on mental health.
She said: "Every day, you get up and go to work so the NHS can continue to do what it has done every day for 70 years - provide the British people with some of the best healthcare in the world.
"I want that to continue.
"But for that to happen we must recognise that the NHS conceived by the likes of Beveridge, Willink and Bevan was created to serve a very different country in a very different time."