Middlemore Hospital is blaming a spate of stabbings over the weekend on holiday-fuelled drinking and stress.
The hospital's emergency department treated four men for stab wounds on Saturday night alone.
Emergency care clinical head Vanessa Thornton said assaults were common at this time of year, because people drank more and money worries came to the fore.
"It's part of the pre-Christmas stress, and alcohol, that seems to fuel fighting and aggression."
She said the department had rostered on more staff to cope with the extra pressure.
Dr Thornton said the closure of local GP surgeries also added to the high demand faced by emergency rooms over Christmas.