He was educated at the Hawick town school and at the university of Edinburgh, and, afterwards studied at Glasgow.

About 1757 he settled at Wooler in Northumberland, and while there was chosen physician of the Bamborough infirmary.

By the advice of Sir John Pringle he went to London in 1777, and shortly after was appointed physician to the eastern dispensary.

A collective edition of his ‘Works,’ with a memoir by his son, William Turnbull, was published in 1805, 12mo.

Turnbull contributed the ‘medicinal, chemical, and anatomical’ articles to the ‘New and Complete Dictionary of Arts and Sciences’ (London, 1778, fol.).