Many elective surgeries and clinics scheduled across the country tomorrow are being deferred in anticipation of 10,000 allied health workers walking off the job for 24 hours.
District Health Boards and the Public Service Association have agreed to retain life-preserving services for the duration of the industrial action.
Efforts to settle pay claims for workers such as lab technicians, physiotherapists, social workers, pharmacists and psychologists have failed.
DHBs contacted by RNZ said some elective surgery and outpatient clinics would be cancelled on Monday but patients should attend scheduled appointments unless they had been contacted.
Emergency departments will remain open.
A Canterbury DHB spokesperson said many of its services would be affected by the strike and waiting times would be longer.
About 100 outpatient and 220 community appointments run by Allied Health staff have been cancelled for tomorrow.
"The 24-hour strike will generally affect the patient flow, in particular, some discharges back to the community where physio, social work, occupational therapy and dieticians are often involved," a DHB spokesperson said.
"Where it is appropriate and safe to do so, we will discharge patients home ahead of the strike to reduce the pressure on those staff who are working."
Only urgent laboratory tests will take place on Monday for life-preserving criteria for critical patients.
Burwood Hospital elective operating theatres will be closed and five operating theatres will be open at Christchurch Hospital for life-preserving surgery.
"We would normally have around 15 surgeries at Burwood and around 90 surgeries at Christchurch Hospital on a Monday; however, it is hard to quantify the exact number of surgical admissions that have been deferred due to the strike action as some surgeries have not been scheduled as they normally would be due to the pandemic response," the spokesperson said.
"We respect the right of staff to take industrial action and acknowledge the important role that health workers play in delivering high-quality care."
Auckland DHB said patient safety remained its priority and it would continue to provide emergency and life-preserving services.
"Please come to your scheduled appointment unless we have contacted you directly to say your appointment is being rescheduled."