Milton Keynes Hospital is currently on ‘Black Alert’ because of an unexpectedly large number of patients needing treatment.
The status means there is significant pressure on staff and the number of beds available for patients.
People are being told to only dial 999 or visit the hospital’s under pressure A&E department in a ‘genuine emergency’.
Hospital Chief Executive Joe Harrison said: “In common with many other local hospitals, Milton Keynes Hospital is currently on black alert.
“Black alert means that the hospital is very busy due to a high number of emergency patients, and experiencing severe pressure with ensuring we have enough beds for our patients.
“Our A&E is particularly busy, and more patients than average have been arriving at our A&E by ambulance. We have measures in place to make sure all our patients receive the care they need as quickly as possible.
“Please help our staff treat those most in need of their care by calling an ambulance or coming to A&E only in a genuine emergency.”
The record number of visitors to the hospital’s A&E was most recently broken in October when 262 people arrived in one day.
That record has not been broken again so far this week, but the increase in pressure has instead come from what the hospital has described as ‘more poorly patients’ than normal.
And the number of ambulances arriving at the A&E is said to be up 10 per cent on the same time last year.