[2] Proceeding to study medicine at Queen's College, Belfast, Whitla took the LAH, Dublin, and the LRCP and LRCS of Edinburgh in 1873.

The pair were married in 1876, setting up house at 41, Great Victoria Street, Belfast, where Whitla established a general medical practice.

He succeeded Seaton Reid as professor of materia medica at the Queen's College in 1890; he was twice president of the Ulster Medical Society (1886–87, 1901–02).

[6] That year the Whitlas moved to Lennoxvale, a suburban mansion, they also retained the professional house in College Square.

[2] He served the British Medical Association as president (presenting each member who attended the annual meeting held in Belfast in 1909 with a copy of his most recent book, The Theory and Practice of Medicine, and entertaining them at Lennoxvale).

Together with his practice and books he had a flair for making wise investments, buying oil shares to his great financial advantage.

As a biblical scholar he contributed an introductory study of the nature and the cause of unbelief, of miracles, and prophecy to an edition of Sir Isaac Newton's Daniel and the Apocalypse[7] published by John Murray in 1922.