People are being asked to avoid A&E at Lincoln County Hospital unless absolutely necessary, following a sudden 'high demand' for beds.
The United Lincolnshire Hospitals Trust says it is having to take action to ease the pressure.
Staff have been put on additional ward rounds to make sure those who are well enough are discharged, to help free up beds.
The hospital says it is also liaising with GPs in the county to make sure patients aren't referred there when they don't need hospital care.
Patients with less severe medical conditions are being treated at community based facilities where possible.
People are being asked to call the NHS 111 number or see a GP or pharmacist for any problems if possible.
Those with minor injuries are being encouraged to see their local walk-in centre before heading to A&E.
However ULHT says "no single incident has caused this pressure" on hospital services.