Trained as a doctor at Edinburgh University, he worked at Birmingham General Hospital from 1779. The story is that one of his patients with dropsy (congestive heart failure) improved remarkably after taking a traditional herbal remedy; William became famous for recognising that the active ingredient in the mixture was contained in the leaves of foxgloves. The active ingredient is now known as digitalis to denote its discovery in foxgloves)
He lived in Edgbaston Hall (now a golf club), in Birmingham, England, and was one of the members of the Lunar Society. He is buried in Edgbaston old church. His memorial stone, now moved inside the church, has foxgloves carved upon it to commemorate his discovery.