The majority of non-urgent elective procedures are to be postponed by NHS Lanarkshire to free up staff and beds for urgent care.
On Thursday, the health board said they had taken the decision due to “unprecedented pressures”.
The postponements will be in place for the “next couple of weeks”, the board has indicated.
Dr John Keaney, NHS Lanarkshire acute medical director, pointed to bed and staff shortages as reasons behind the pressures faced.
“The sustained pressure we are seeing across our three acute hospitals is showing no signs of easing and our staff are struggling to cope,” he said.
“We are facing relentless pressures, bed shortages and staff shortages due to sickness, stress and self-isolation.
“Unfortunately we are having to postpone the majority of non-urgent procedures and I would like to apologies to those patients affected.
“Most patients will receive a text message confirming the postponement of their appointment. A small number of appointments will still go ahead as scheduled based on clinical priority.
“Cancelling this inpatient activity will release bed capacity and staff to support our A&E department which is currently seeing an unprecedented level of activity.”
NHS Lanarkshire has said that patients will receive a letter, text message or voice message giving details of any cancellation, postponement or new appointment.
Appointments for urgent referrals, including cancer referrals, maternity and neonatal clinics have continued throughout the pandemic.
Dr Kearney added: “We continue to see people attend A&E for conditions that would be best treated elsewhere.
“We are asking people to please keep our A&E departments safe for those who need critical care.
“If you think you need to attend A&E but it’s not life-threatening, you should consider the alternatives.
“You can call NHS 24 on 111 day or night, where you will be directed to the right NHS service. If you just need health care advice, then please use the NHS Inform website.”