The government hopes to cut hospital deficits in England by reducing the number of emergency admissions for chronic illnesses.
Heart patients could be treated at home
The health secretary is set to announce patients with illnesses like asthma and heart disease could be better cared for by community nurses in their own homes.
The measures are intended to save the NHS more than £400m a year.
But nursing leaders said ministers must first ensure staff levels are adequate, which will require further funding.
"We're very supportive of care moving from the hospital to the community but there's got to be the capacity," said Dr Beverly Malone, general secretary of the Royal College of Nursing.
"We're talking about a number of health visitors, a number of school nurses, a number of community matrons and practice nurses, and we're talking a good several hundred at least. It's not a cheaper alternative."
It is staff costs that have contributed to the record overspend of up to £800m predicted for NHS hospitals in England this year.
The problem has been caused partly by more expensive drugs but mostly by a big increase in wage packets, the cost of which the government admits it underestimated.
Dr Mike Knapton, a Cambridge GP and spokesman for the British Heart Foundation, told BBC News 24 that the move might save some money.
He said: "I'm aware that at times, as a GP, I'm sending patients into hospital for the want of relatively modest resources to look after them for a few days, during acute exacerbation of their illness.
"So it might save money, but that, for me, is not the starting point. For me, the starting point is making sure the quality of care for these patients with long-term conditions is improved, they're looked after in their homes, and it's safe."
Advice up front
The NHS spends £1.3bn a year on admissions for patients with 18 common conditions. Those in this group can be admitted to hospital three or more times in a year, costing up to a quarter of a hospital's expenditure in some regions, according to the Department of Health.
Some 5.2m Britons have asthma
In Monday's announcement, Ms Hewitt will say that if unplanned emergency admissions can be reduced by 30%, hospitals could plan their services better - with potential savings averaging almost £2.5m for each primary care trust.
Asthma UK's chief executive, Donna Covey, said it was important to give sufferers better information when first diagnosed. Personal action plans help asthma sufferers manage their disease, yet fewer than one in four of the UK's 5.2m sufferers have one.
"It takes 20 minutes on average for a health care professional to talk somebody through an asthma action plan, but what you get back in that is fewer hospital admissions, fewer unexpected attendances at the GP.
"One of the things we need to see is ways in which people get more time up front so they're taking up less time and less money and less of their lives further down the line."
On Friday, a hospital trust with a £17m black hole announced it was cutting 1,000 jobs. Responding to this news, Ms Hewitt rejected claims that this indicated patients would suffer because of the cash crisis.
She said efficiency savings, such as reducing administration costs and increasing the number of day operations, could be made without affecting patient care.
Ministers have already said that NHS trusts are to be rated separately on financial management, in addition to patient care, as part of measures to tackle those using resources poorly.