An economic depression, hyperinflation in the Weimar Republic, forced his father to abandon publication at Halle, and his family moved to Dresden in 1923.
Soon after enrolling in a medical course at the University of Freiberg in Breisgau, his father died and moved to Frankfurt to live with his uncle and study there.
Moving to Switzerland, he submitted his already finished thesis on gastric secretion titled Salzsauräproduktion in Sauglingsmagen nach Histaminreiz.
[1] He was appointed as a research assistant to Otto Fritz Meyerhof (winner of the Nobel Prize in Physiology and Medicine in 1922) at the Kaiser Wilhelm Institute in Heidelberg.
Meyerhof arranged for his visit to the University of Cambridge in 1935, where he met Frederick Gowland Hopkins, winner of the Nobel Prize in Physiology or Medicine in 1929.
Charles Scott Sherrington, Nobel laureate and former President of the Royal Society, help him get a position in the Emergency Medical Service at Runwell Hospital in Essex.
He was initially a pathologist, raised to Lieutenant Colonel and later appointed assistant director of pathology to the North East India Command.
[1] His major works in the biochemistry of blood originated there as he witnessed high incidence of iron deficiency among the Indian troops.
He retired from the university in 1977, and continued a research programme called the National Haemoglobin Reference Centre funded by WHO.
[4] In 1940, Lehmann married Benigna Norman-Butler, a musician, with whom he had two daughters, Susan and Ruth, and two sons, Paul and David.
[6][7][8] His next major work was the case of pseudocholinesterase deficiency, a deadly blood disease in which individuals have severe sensitivity to certain anesthetic drugs.
[16] He was credited as "more than anybody responsible for cataloguing the enormous wealth of variations in the hemoglobin mutants and setting our base of understanding of the population genetics, anthropology, and clinical diversity of the structural variants.
[4] He won the Rivers Memorial Medal of the Royal Anthropological Institute in 1961 for his studies of sickle cell disease in the Andaman Islands.