Around 100,000 nurses are striking today in the first major walkout in a century.
The Royal College of Nursing has released the list of trusts impacted by the historic action, with 44 out of 219 NHS trusts in England voting in favour of action.
In Wales, staff in six out of seven health boards and all six trusts in Northern Ireland will also go on strike.
Nursing staff working outside of hospitals, such as those in commissioning organisations called integrated care boards, also voted to take action.
The union is set to hold a second strike day on Tuesday 20 December.
NHS trusts across England, Wales and Northern Ireland will be negotiating with union reps in the week ahead over staffing levels over which services they can maintain.
What NHS services will be impacted by strikes?
Planned operations such as knee and hip replacements, community nursing services and health visiting are likely to be badly hit by the strikes.
Some cancer treatments, mental health services and urgent testing may be running at a reduced service.
According to NHS England, emergency care will continue to be available throughout the strike days. People who are seriously ill, injured or whose life is at risk should seek medical attention in the normal way by calling 999 or going to A&E.
GP services, dentists and community pharmacies will be running as normal.
Full list of trusts facing strikes in December:
England
Kettering General Hospital NHS Foundation Trust
Northamptonshire Healthcare NHS Foundation Trust
Nottingham University Hospitals NHS Trust
Nottinghamshire Healthcare NHS Foundation Trust
Cambridge University Hospital NHS Foundation Trust
Cambridgeshire and Peterborough NHS Foundation Trust
Cambridgeshire Community Services NHS Trust
Hertfordshire Community NHS Trust
Royal Papworth Hospital NHS Foundation Trust
Great Ormond Street Hospital for Children NHS Foundation Trust
Guys and St Thomas NHS Foundation Trust
Imperial College Healthcare NHS Trust
Royal Marsden NHS Foundation Trust
Alder Hey Children’s NHS Foundation Trust
Liverpool Heart and Chest Hospital NHS Found Trust
Liverpool University Hospitals NHS Foundation Trust
Liverpool Women’s NHS Foundation Trust
Mersey Care NHS Foundation Trust
The Clatterbridge Cancer Centre NHS Found Trust
The Walton Centre NHS Foundation Trust
Gateshead Health NHS Foundation Trust
Northumbria Healthcare NHS Foundation Trust
The Newcastle Upon Tyne Hospitals NHS Foundation Trust
Oxford Health NHS Foundation Trust
Oxford University Hospitals NHS Foundation Trust
Royal Berkshire NHS Foundation Trust
Devon Partnership NHS Trust
Gloucestershire Health and Care NHS Foundation Trust
Gloucestershire Hospitals NHS Foundation Trust
Great Western Hospitals NHS Foundation Trust
North Bristol NHS Trust
Royal Devon University Healthcare NHS Foundation Trust
Royal United Hospitals Bath NHS Foundation Trust
Torbay and South Devon NHS Foundation Trust
University Hospitals Bristol and Weston NHS Foundation Trust
University Hospitals Plymouth NHS Trust
Birmingham Women’s and Children’s NHS Foundation Trust
Herefordshire and Worcestershire Health and Care NHS
The Royal Orthopaedic Hospital NHS Foundation Trust
West Midlands University Hospitals Birmingham NHS Foundation Trust
Worcestershire Acute Hospitals NHS Trust
Bradford Teaching Hospitals NHS Foundation Trust
Leeds Community Healthcare NHS Trust
The Leeds Teaching Hospitals NHS Trust
Wales
Cardiff and Vale University Health Board
Powys Teaching Local Health Board
Hywel Dda University Health Board
Swansea Bay University Health Board
Cwm Taf Morgannwg University Health Board
Betsi Cadwaladr University Local Health Board
Northern Ireland
Southern Health and Social Care Trust
Western Health and Social Care Trust
Belfast Health and Social Care Trust
Northern Health and Social Care Trust
South Eastern Health and Social Care Trust
Northern Ireland Ambulance Service
