Northern Ireland's Health and Social Care Board is urging people to avoid emergency departments unless they're seriously ill or injured.
A spokesperson said wait times have risen beyond what's "acceptable" as services treat an increasing number of children and elderly with complex conditions.
They said health services face a "challenging winter".
A spokesperson for the health system said: “Emergency Departments across Northern Ireland continue to be extremely busy with increasing numbers of children and older, sicker people with complex conditions attending and being admitted.
“We would therefore ask the public to assist us in using services appropriately. Our clear message is if you are seriously ill or injured, then the Emergency Department is the place to go."
They said patients deemed as non-urgent would face lengthy waits.
“If you do not need emergency care, we would urge you to please choose alternative services. These include using the online A-Z symptom search ( click here ), seeking advice from your local pharmacist, contacting your GP, or the GP Out of Hours services (if your medical condition can’t wait until your GP surgery reopens).”
“The public can access waiting time information at all EDs and Minor Injury Units across the region by logging onto www.nidirect.gov.uk/emergency-department-waiting-times . This NI Direct web page is updated hourly.”
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