A so-called "Brexit Dividend" will see extra cash flow to the NHS from the more than £9 billion a year the United Kingdom now sends to the European Union, according to Mrs May.
But critics have condemned the announcement, saying that there will be no money at all from a "Brexit Dividend" because of the damage Brexit will do to the United Kingdom economy. But she that "we as a country will contribute a bit more" - meaning ministers will have to raise taxes or borrow more to find the money.
"The (Office for Budget Responsibility) has said by £15bn; it could be a bit more, it could be a bit less".
"This long-term plan and historic funding boost is a fitting birthday present for our most loved institution".
"As a pure, sort of arithmetic point of view, over this period, there's no money".
Coming in at £384 million extra a week, it trumps the controversial £350 million a week increase promised by the now infamous red Leave campaign buses during the European Union referendum.
But when pressed further about where the extra funding would be coming from, she said: 'It is right, I think, that we say to people that because the NHS is so important to us that we do look at asking for the country to contribute more, but in a fair and balanced way.
As part of the initiative, the health service will draw up a long-term plan led by doctors setting out how the resources should be best used.
What kind of cash injection is the NHS getting?
"Today's announcement on funding is nowhere near good enough and the Prime Minister has confirmed there is no new money for social care". Extra taxes and borrowing will likely be needed. "She won't stand up to vested interests and is instead asking patients to rely on a hypothetical Brexit dividend".
Meanwhile Commons Health Committee chairwoman Sarah Wollaston said she was sad to see the Government "slide to populist arguments" as people were being "treated like fools". He said: 'As the NHS turns 70, we can now face the next five years with renewed certainty.
The five-year settlement is part of a 10-year plan for the NHS for key improvements in cancer, mental health and other critical services.
Wollaston tweeted: "The Brexit dividend tosh was expected but treats the public as fools. This will make it harder to have a rational debate about the "who & how" of funding & sharing this fairly".
"And the invitation to the NHS to develop consensus proposals for legislation will help accelerate the move to more integrated care, and ensure taxpayers' money is spent to maximum benefit".