Canterbury District Health Board is facing its worst shortage of nurses, with 200 positions currently unfilled across the district.
The shortage means remaining staff are working longer hours to cover and has also forced the postponement of some surgery.
A total of 87 jobs are unfilled in the medical and surgical division alone.
The shortage is attributed to a variety of reasons: from winter illness to a change in modern living that has seen more staff opt for casual contracts rather than fulltime jobs.
The district health board is trying to juggle rosters and is reviewing how it uses other staff.
The New Zealand Nurses Organisation says the problem is not unique to Canterbury, as there is an international nursing shortage, and other health boards have the same problem.
It says there is no quick fix, but says it is working with district health boards across New Zealand to find short-term solutions to ensure remaining staff do not burn out.
Nursing director at Christchurch Hospital, Jackie Flynn, says a return-to-work training programme is under way to help former nurses back into the workforce, but there is any level of shift work available for qualified staff.