Thomas Fraser graduated in medicine from Aberdeen University in 1898. In the early 1900s he and John Rennie, a zoologist, studied the effects of giving patients with diabetes extracts of fish pancreatic islets of Langerhans. In the patients they studied no benefits were found, but their work was an important part of the movement that led to the discovery of insulin in 1922.
In the first world war he served with distinction in Egypt, Gallipoli and France, earning the DSO and being mentioned in dispatches five times. There followed a distinguished career as a physician in the Royal Infirmary and lecturer in the medical school. He was president of the British Medical Association from 1939 to 1942. He is commemorated by a plaque at 16 Albyn Place.