Gary graduated from Monash Medical School in 1997 with honours. He undertook basic physician training at the Alfred Hospital and then went on to complete advanced physician training at the Royal Melbourne Hospital. He obtained a combined fellowship from both the Royal Australasian College of Physicians and the Royal College of Pathologists of Australasia in 2007. He's a Consultant Clinical Immunologist and Allergist in the Department of Clinical Immunology and Allergy at The Royal Melbourne Hospital where he was the Head of the Immunopathology Department from 2008 until 2015. Gary is also a Consultant Pathologist at Melbourne Pathology.