McBain completed her medical training at Dalhousie University in Nova Scotia.
[1] McBain found she enjoyed teaching medical students that came to the medical centre, and she joined the faculty of the University of Otago in 1995 as a part time lecturer, rising to associate professor in 2018 and full professor in 2024.
[2][3] McBain has been the head of the Department of Primary Health Care and General Practice since 2017, and was appointed Deputy Dean at the University of Otago Wellington campus in 2022.
[2][4] McBain's research focus cover both medical education and clinical practice.
[1][4] McBain was appointed a Distinguished Fellow of the Royal New Zealand College of General Practitioners in 2011.