Visitors are being asked to stay away from the Royal Lancaster Infirmary, in a bid to control a fresh outbreak of the winter vomiting bug, norovirus.
The hospital issued a similar appeal in February when all but five wards were closed by the University Hospitals of Morecambe Bay NHS Foundation Trust.
Jackie Holt from the trust said people should stay away unless the visit was "absolutely necessary".
"These precautions are to protect our patients and staff," she said.
She added: "If you have to visit, please ensure that you contact ward staff to discuss before you visit and do not bring any babies, children or vulnerable people with you.
"This is especially important if you are planning on visiting intensive care units, small babies, children or people undergoing treatment for cancer or blood disorders."
The bug - which causes vomiting, stomach cramps, fever and diarrhoea - is easily spread from person to person.
Symptoms usually begin between 12 to 48 hours after a person becomes infected, with most healthy people making a recovery within one to three days.