So hospitals have announced that they're on 'black alert' - but what does this actually mean?
This is the highest level of alert, which usually means bed capacity has been reached and that patients arriving at A&E will have to be taken to another hospital. Sometimes routine operations will be cancelled to free up bed space.
NHS England classifies a black alert as a "serious incident". It means the system is under severe pressure and is unable to deliver certain actions and comprehensive emergency care.
It also means there is potential for emergency care and safety to be compromised. Decisive action must be taken to restore the hospital's capacity and ensure patient safety.
A woman discharged herself from Yeovil hospital after an operation on Monday. She says it was too busy for her to stay.
Southmead Hospital, the BRI, Bristol Royal Hospital for Children and Weston General Hospital have announced that they are on black alert.