Staff from hospitals in Boston, Lincoln and Grantham are being asked to cancel their leave
Hospital staff are being asked to cancel their leave and return to work because hospitals in Lincolnshire are busier than anticipated over Christmas.
Patients are waiting on beds in A&E because there is no space on wards, staff are "becoming quite tired" and A&E waiting times are "very difficult".
Registered nurses and healthcare support workers are most in demand.
Lincolnshire East Clinical Commissioning Group's chief nurse said they needed as many as possible.
"Even a few hours' help would be incredibly helpful for us at the moment," said Tracy Pilcher.
"Obviously our A&E departments are very busy and our staff that are working have been working over the last few days and are becoming quite tired."
She said staff who usually work at Lincoln County Hospital, Grantham and District Hospital, and Pilgrim Hospital, in Boston, should get in contact and go to their operations centres so they can be deployed to appropriate wards.
Busier 'across country'
Staff are "working in a situation where all our hospital wards are full", but Ms Pilcher said Lincolnshire was not the only place experiencing problems.
"I think across the country it's been a lot busier over the Christmas period than we had anticipated, and a lot busier than last year," she said.
The problems have been attributed to more patients coming in than predicted, and these people were more ill than usual, meaning they were stopping in hospital for longer.
There are also problems with "bed-blocking", where patients are well enough to leave hospital but there are delays in discharging them.
"The way that Christmas fell, and then we had a weekend, we've got patients in the hospital that we would like to discharge home but currently can't find the support to enable us to do that," said Ms Pilcher.
29 December 2014 Last updated at 14:15