Figures supplied in response to a request from the Otago Daily Times showed overtime payments for nurses and medical staff were over budget by almost $6 million for the past three financial years.
"It is expensive for the district health board and not good for staff to continue to work over their normal hours."
Recruitment was a high priority and the board was doing all it could, Mrs Blake said.
Overtime payments rose from $1.9 million in 2005-06 to $3 million in 2007-08.
The board's overtime budget was $1.5 million for the three-year period.
The amount of overtime paid to senior doctors more than doubled over the past three years, while overtime paid to junior doctors increased 58% and nurses increased 55%.
Nurses received the largest chunk of overtime payments at $3.5 million over three years, closely followed by junior doctors at $3 million. Senior doctors were paid almost $1 million in overtime.
New Zealand Nurses Organisation Otago representative Lorraine Lobb said working a lot of overtime made people tired, increased their sick leave and lead to an increased danger of making a mistake.
"Mental health is by far the biggest contributor to this, I would say. They have had the largest vacancies and I know there has been lots of overtime in that area."
Staff vacancies were also becoming a problem in the general area, she said.
Nursing shortages were a national and international problem.
Association of Salaried Medical Specialists Otago representative Dr Chris Wisely said shortages could have a snowball effect, as short-staffed areas, where working conditions may not be ideal, were harder to attract new recruits into.
One senior doctor recruited from the United Kingdom was considering returning home after finding his lifestyle was no better in Dunedin, Dr Wisely said. He was devastated at how little time he has been able to spend with his children.
Mrs Blake said the board was planning another recruitment drive in the United Kingdom in October. A similar drive last year jointly cost the Otago and Southland boards $140,000, but had already paid for itself in terms of successful recruitment.
In a report to the board last month, Mrs Blake said there were about 58 nursing vacancies, 24 senior doctor vacancies and no junior doctor vacancies, as at July 30.
