The largest strike in NHS history will begin at 08:00 on Thursday and involve nurses in England, Wales, and Northern Ireland.
The provision of “life-preserving” care will continue, as will some urgent care, but routine surgery and other planned treatments are likely to be interrupted.
After ministers declined to resume salary negotiations, the Royal College of Nursing claimed that staff had no choice but to accept the situation.
The RCN’s demand for a 19% wage increase was deemed unaffordable by the UK government.
Around a fourth of England’s hospitals and community teams, all of Northern Ireland’s health boards, and all but one of Wales’ health boards will be involved in the action. In Scotland, nurses are not on strike.
Under trade union laws, the RCN has to ensure life-preserving care continues during the 12-hour strike.
Chemotherapy and kidney dialysis should run as normal, along with intensive and critical care, children’s accident and emergency and hospital neonatal units, which look after newborn babies.
Beyond that, it will be up to NHS boards and trusts to negotiate services on a local level, with discussions likely to come down to the circumstances of some individual patients.
The biggest impact is likely to be in pre-booked treatment such as hernia repair, hip replacements or outpatient clinics.
The NHS has said it is “vital” people continue to come forward for emergency care during the strikes and anyone not contacted to reschedule an appointment should attend as planned.
The RCN balloted more than 300,000 nurses across individual NHS trusts and boards rather than in a single, national vote.
This means some nurses are not entitled to take industrial action, because the turnout in their local area was too low.
In England, the first round of strikes will go ahead in 51 of 219 hospitals, mental-health trusts and community services.
Strikes are also going ahead in all of Northern Ireland’s health boards and all but one in Wales, the Aneurin Bevan.
Most GP services will be unaffected, as nurses working directly for practices were not entitled to take part in the vote, but the strike will include district nurses working in people’s homes or community settings.
A second day of strike action will go ahead on 20 December, unless there is a breakthrough in talks.
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