Magnus had five children, Karl (1903-1989) lung specialist; Margarete (Gretl)(1905-1968)who worked as his secretary and translator; Dorothea who died aged 11; Erica (1909-1991) architect; and Otto (1913-2014) neurologist.

The pharmacological research of Rudolf Magnus was focussed on the effect of medication on the heart, blood vessels, lungs and the gastrointestinal tract.

He conducted the poison gas study during World War I (1914—1918) when he served as an army doctor in Germany.

Magnus was very fond of ice skating and would give his whole laboratory staff time off when the temperature was below freezing.

Originally the pharmacology department in Utrecht was housed in an old hospital for victims of the plague (built in 1567), named Leeuwenbergh.

In 1926, Magnus laid the first stone for this new institute in Utrecht on the Vondellaan, named Nieuw Leeuwenbergh.