Known as Dr Prem to his patients, Dr Prematilake is from Sri Lanka and earned his MBBS in 1992. In 1999 he obtained MD (medicine) from the University of Colombo to become a general physician in Sri Lanka.

Coming to Australia, Dr Prematilake received a training position in the department of Gastroenterology in the Alfred Hospital in Melbourne in 2000. He subsequently continued his physician and gastroenterology training in Frankston Hospital, Box Hill Hospital and Ballarat Hospital in Victoria and Launceston Hospital in Tasmania. He then moved to New South Wales and has worked at John Hunter and the Marta Hospital in Newcastle.

Dr Prematilake completed his physician training and gastroenterology training program in 2008. He earned his FRACP in 2007 from the Royal Australasian College of Physicians with dual certification to practice both internal medicine and gastroenterology.

Dr Prematilake has been a visiting physician and gastroenterologist locally at Manning Base Hospital Taree since 2009.

Dr Prematilake is a member of the Gastroenterology Society of Australia, American Gastroenterology Association and Gastroenterology Association of Sri Lanka. He is also a member of American College of Physicians and is a conjoint lecturer at the University in Newcastle.

Dr Prematilake is employed as a general physician and gastroenterologist in Manning Base Hospital and has a private practice in Taree and Foster, which operates from the Gastrointestinal and Liver Clinic Taree.

Dr Prematilake visits Forster on Mondays and Thursdays every week, with the rest of his time spent in his Clinic in Taree.

He performs gastroscopy and colonoscopy procedures at Forster Private Hospital, Mayo Private Hospital and Manning Base Hospital.

Dr Prematilake performs pilcam (videocapsule endoscopy) and Fibroscans and abdominal US scans in his Taree rooms.