Rotorua Hospital has reached capacity on Sunday and people are being asked to only go to the Emergency Department in case of a "real emergency".
The hospital is not expecting to have many discharges, and with patients already waiting in ED until a hospital bed is available, the situation is not expected to improve quickly, a statement from Lakes District Health Board says.
Many of the hospital admissions are for patients with winter-type illnesses, including bronchiolitis, asthma and influenza.
Hospital staff say a number of people coming into the ED would be better placed heading to Lakes PrimeCare, the after-hours medical centre in Rotorua.
Dr Vijay Thumma from Rotorua ED says people with flu-type symptoms are often better off staying at home, tucked up in bed with plenty of fluids and paracetamol. If symptoms persist or get worse, then he suggests people make an appointment to see their GP during the week.
He adds with the onset of flu season, it's also really important to remember the basics, like covering your cough and washing your hands often, to stop the spread of germs. Most importantly he says people should stay home from work and school.
Medical advice is also available by telephone if you or your whānau are unwell. The free service is available 24/7 on 0800 611 116.