He was born in Bergen as the son of merchant Fredrik Georg Gade (1830–1905) and his wife Ingeborg Wallem (1830–1902).

[3] Gade was a skilled amateur violinist, and played together with composer and conductor Iver Holter while studying.

He also befriended cultural and political personalities such as Edvard Grieg, Georg Brandes, Jonas Lie, Alexander Kielland and Christian Michelsen.

[3] In 1900 he had been considered as the replacement of professor Hjalmar Heiberg, but since Gade did not hold a doctorate, the position went to Francis Harbitz.

[3] In addition to his academic work, he also wrote popular-scientific books, including 1929's Kreftsykdommene, deres vesen, utbredelse og bekjempelse.

He edited the journal Norsk magasin for lægevidenskaben from 1893 to 1897 and 1912 to 1927,[1] and engaged himself in the public debate, siding with the political liberals of the day.

The Gade Institute at Haukeland Hospital, a forerunner of the Faculty of Medicine at the University of Bergen, is named after him.