A major refurbishment of the emergency department at St Mary's Hospital will be carried out over the next six months.
The work will include increasing the number of 'major' beds and an additional resuscitation bay will be provided.
A re-fit of the areas used by patients who require suturing or plastering will be carried out and a new two-bedded area with en-suite facilities and relatives room will be created.
Donna Collins, associate director for the Acute Clinical Directorate, said: "This is an exciting development that will unquestionably improve facilities and services for our patients.
"We are working closely with contractors to ensure disruption to patients is minimal.
"The majority of the work is being carried out by Island firms, who will work extended hours to ensure the work is completed as soon as possible.
"It may be noisy at times during the day which is unavoidable but this will avoid disruption at night by the contractors.
"We ask the public to bear with us during this major refurbishment, and consider carefully if they really need to come to the emergency department.
"Around 50,000 patients are seen by the department each year, and of these last year, 9,174 received no significant treatment and could therefore have been seen by their own GP, local pharmacy or the Beacon Centre."
The work will be undertaken over several phases in order to minimise disruption to the department.
Robin Beal, clinical lead, said the six month period of disruption was necessary to provide significantly improved facilities for the care of those patients who were acutely ill or had undergone traumatic injury.
He said: "Fortunately, the result will give us a department designed to improve the observation of patients and more space to deal with the ever increasing demand."
Temporary portacabins will be located at the front of the department during the building works, and visitors to the department will notice different areas being partitioned off during the six-month period.