Patients in Sheffield are being urged to attend their appointments as normal during a strike - but are warned there could be longer waits.
Health staff, not including doctors, are to rally outside the Northern General Hospital on Monday morning in a walkout over pay.
Ambulances will be able to attend emergency or priority incidents only, and Sheffield Teaching Hospitals NHS Foundation Trust says it may take time to get services up to speed.
Clinically urgent and emergency care - including A&E, operations, chemotherapy, radiotherapy and dialysis - will continue as normal, after work with union chiefs to minimise disruption.
Ellen Ryabov, chief operating officer at Sheffield Teaching Hospitals NHS Foundation Trust, said: “We respect the staff decision to strike or not, but our first priority is patient safety and ensuring there is as little disruption to services as possible.
“For non urgent appointments and procedures we are asking patients to turn up as planned and, if there is any change to their appointment, we will contact them direct.
“In the unlikely event an appointment has to be postponed we will re-arrange it as soon as possible.
“We have put plans in place to try to limit disruption and inconvenience for patients but it is likely that, while the strike period is due to end at 11am, we may take some time to get our services back up to normal speed, and we would ask patients to be aware there may be longer than normal waits to be seen. We will endeavour to keep all patients informed of wait times.
“Yorkshire Ambulance Service confirmed they will also be affected and can only guarantee the provision of emergency or priority ambulances during the strike.”