Cardiff and Vale University Health Board has tonight asked local people for support and to think twice before coming to the University Hospital of Wales' Emergency Unit.
It follows what they call an unprecedented influx of patients over the past 48 hours.
UHB Medical Director Dr. Graham Shortland said the health board was asking for support from the public to reduce the pressure on clinical teams, so they could focus on caring for the sickest patients.
While the sickest and most vulnerable patients are being seen promptly and there are no significant ambulance delays, we would like to ask local people to help us by not coming to hospital with minor illnesses or minor injuries that can be easily dealt with.
Patients who do come to the Emergency Unit with these minor conditions can expect significant waits for treatment, because we are mobilising our resources and focusing our energies on those patients with the greatest clinical need.
This is not a new message, and we ask people throughout the year to make sensible use of the Emergency Unit, but this is even more important when we have so many seriously ill patients at this time of year who need our care the most.”