NHS staff take twice as many days off sick a year as private sector workers, it is reported.
A survey of health trusts in England by the NHS's Information Centre found they lost an average of 4.5% of working time to sick leave in 2005.
Nursing Standard magazine reports that this equates to NHS employees taking an average of 12 days off sick a year.
Bosses' organisation NHS Employers is to launch a drive to reduce the number of staff on long-term sick leave.
Figures from the CBI suggest the average absenteeism rate in the private sector is six days a year
The survey also found that health service staff in the north east and north west were most likely to take sick days.
A total of 5.3% of working time was lost to sickness absence in the north east, compared with 4.1% in London and the south east.
Overall, health service sickness absence rates have fallen slightly from 4.7% in 2003.
Trusts that provide frontline services had the highest rates of sick leave.
People working for the ambulance service had most days off due to sickness, with an absence rate of 6%.
Hospital trusts recorded an absence rate of 4.4%. Staff working in the administrative, strategic and special health authorities were least likely to be away ill (2.8%).
A separate joint survey by the Confederation of British Industry and insurance group AXA found absence levels were 30% higher across all public sector organisations than in the private sector.
Julian Topping, NHS Employers' head of workplace health, said a crackdown on short-term sickness absence and the introduction of flexible working had contributed to a steady but slow reduction in overall NHS sick leave rates.
"This is a big achievement, especially when you remember that the NHS is a 24 hour service and, by its very nature, is a more risky place to work than many private sector companies.
"However, NHS Employers is determined to reduce staff sickness absence even further.
"Our next target is to tackle long-term sickness by improving the rehabilitation of staff.
"We are also carrying out a joint review with trade unions of how staff sickness and injury is managed in the NHS."
Richard Diment, chief executive of the Ambulance Service Association, said the stress of dealing with potentially traumatic situations might have contributed to a higher absenteeism rate among his members.
However, he said the most significant factor was likely to be the greater risk of physical injury.
"A lot of investment has been made in equipment and training to try to reduce the amount of manual handling involved in the job," he said.
"But the reality is that ambulance workers are still sometimes going to have to face situations such as moving a heavy patient down a difficult narrow stairway."
A Royal College of Nursing spokesperson said nursing could be a physically and emotionally demanding job.
"It's important that staff feel supported, for example via good access to counselling and occupational health services."