Creutzfeldt was born into a medical family in Harburg, which was incorporated into Hamburg in 1937. In 1903, at the age of 18, he was drafted into the German army and spent his service stationed in Kiel. Afterwards, he attended the School of Medicine of the University of Jena and the University of Rostock, receiving his doctorate at the latter in 1909. Part of his practical training was undertaken at "St. Georg" – Hospital in Hamburg. After qualification he sought adventure as a ship's surgeon, voyaging the Pacific Ocean, taking the opportunity to study local crafts, linguistics, and tropical plants.