Seven of the country's 20 DHBs owe greater than 40 per cent of their staff more than four weeks' leave, with one DHB topping 50 per cent.
Medical specialists have raised concerns about hospital understaffing leading to substandard care.
Association of Salaried Medical Specialists director Ian Powell said over-stretched staff under increasing pressure put patient safety at risk.
He said a recent survey by the association had revealed sick staff were coming to work when they should be at home, including one doctor who was being treated in the emergency department between seeing her own patients.
Public Service Association national secretary Erin Polaczuk said staff were not taking leave and some were working double shifts to cover roster gaps.
Despite this, the Ministry of Health is asking DHBs nationwide to save $163.5 million this financial year.
Labour health spokeswoman Annette King said the move to compel savings from health boards came after years of pressure from central government.
"They've squeezed this lemon so hard the efficiency gains are going to be so difficult to find."
Northland DHB is forecasted to save $5 million this financial year, but Mr Cheong ruled out reducing staff numbers or hours.
Instead, the health board has saved money by relocating off-campus staff to the main hospital, reducing energy bills and by selling extra vehicles.
Official Information Act documents obtained by the Labour Party show most health boards are aiming for multimillion-dollar cutbacks, four of which are hoping to save more than $10million dollars each. Waikato DHB has a savings target of $43million - 4.4 per cent of its almost billion-dollar budget.
Health Minister Dr Jonathan Coleman said in a statement the health budget was at a record high of $15.9 billion. He said it was $400 million more than last year and there have been no funding "cuts".
