An annual budget of £100 billion may sound like a lot but it only stretches so far.
That's why a small group of medical experts face the unenviable decision of choosing which drugs should be available free on the NHS.
The agonising task falls to 26 doctors and professors from across the country sitting on each of the National Institute for Clinical Excellence's (NICE) appraisal committees.
It's not a role they take lightly judging by the huge swathe of publications relating to a single drug, erlotinib - the lung cancer treatment Whitton gran Margaret Whitby has been refused by NHS Hounslow.
The panel has been debating whether to approve the drug for more than three years, with a final ruling due next month. The latest interim guidance, published last month, runs to a hefty 29 pages before concluding the pills are not cost-effective.
A spokeswoman for NICE described the decisions it has to make as 'some of the hardest in public life'.
"NHS resources are not limitless and we have to decide what treatments represent best value to the patient as well as the NHS," she added.
Until NICE issues its final guidance, patients are at the mercy of their local health trusts like NHS Hounslow - leading to what critics describe as a 'postcode lottery'.
In the case of erlotinib (commonly known as Tarceva), NICE's latest advice is that the drug is 'more expensive and less effective' than the alternative docetaxel.
According to September's report, a typical course of treatment with erlotinib costs £6,800, compared with just over £5,000 for docetaxel. Erlotinib also increases life expectancy by an average of eight and a half months - a month less than its competitor.
However, Tarceva's manufacturer Roche claims its treatment is cheaper to administer and has fewer serious side-effects like alopecia and blood disease neutropenia, saving the NHS more money.