Despite his mother's death and him becoming an orphan at the age of fifteen, Kollwitz was able to graduate from high school, enter the University of Königsberg, receive a medical education and a doctorate degree.
[1] After his marriage in 1891 to the artist Käthe Schmidt, Karl moved with her to Berlin, where he opened his medical practice in the Prenzlauer Berg area.
In 1913, Kollwitz and his colleagues Ernst Simmel and Ignaz Zadek founded the Social Democratic Association of Doctors (later the Society of Socialist Physicians).
After the November Revolution in 1919, he became involved in Berlin local politics as a city councilor for the SPD and later as a member of the Internationaler Sozialistischer Kampfbund.
[1] After his death in 1940, Karl Kollwitz was buried in the family grave at the Friedrichsfelde Central Cemetery, next to his brother-in-law Conrad Schmidt and his wife Anna.