In May, the hospital had a 98% occupancy rate, while the optimal rate was 85%.
The past two autumns had been busier than usual. The hospital also recorded 98% occupancy in May 2011.
The DHB is concerned about steadily increasing demand at the emergency department (ED), which had not been fully explained.
While the rate of admissions from ED was steady, there were more patients seen in ED and thus being admitted, operations manager Megan Boivin said.
Access to GPs was thought to be part of the reason.
Ms Boivin said some people being admitted to the hospital from the ED were indicating anecdotally they had not been able to get an appointment with a GP.
While this might suggest a lack of GPs, it could also mean people were putting off making an appointment until the last minute.
Chief nursing and midwifery officer Leanne Samuel said people should not put off going to their GP, because in doing so they risked their condition becoming acute.
The DHB is also encouraging people, especially those in high-risk groups, to get a flu jab.
Ensuring children had their full complement of vaccines also helped prevent diseases like whooping cough, Ms Samuel said.
Members of the hospital advisory committee, and the full board, expressed concern about the situation at meetings in Dunedin last week.
