Some patients are being moved out of the Royal Cornwall Hospital at Treliske as the site continues to deal with an outbreak of a vomiting bug.
Those unaffected by the norovirus are being moved to other Cornwall hospitals to free up beds at the Treliske site.
Health chiefs will review the timetable for non-urgent surgery on Monday to ease the pressure on services.
Visitors are also being asked to stay away unless they are coming to see a critically ill patient.
Minor injuries plea
Six wards are closed to new admissions and five have bays where patients are being kept isolated.
Visits are being restricted to the West Cornwall Hospital in Penzance and St Michael's in Hayle to try to prevent the virus spreading to them.
Director of Nursing, Christine Rashleigh, said: "We are working with our colleagues in primary care and social services to avoid admissions to hospital wherever possible.
"We are in contact with local GPs and would also urge people with minor injuries and ailments to make use of their local minor injury unit rather than coming to the main emergency department at Treliske or casualty at West Cornwall Hospital."
The symptoms of the norovirus infection usually begin around 12 to 48 hours after a person has become infected. It starts with a sudden onset of nausea and is followed by vomiting and diarrhoea.