Rudolf Schoenheimer received his early education in local schools and graduated from the Realgymnasium in 1916. After military service he began the study of medicine at the University of Berlin, receiving his degree in 1922. Recognizing his deficiency in biochemical knowledge, he then studied at the University of Leipzig under a Rockefeller Foundation fellowship for three years.
Drafted into the German army, Rudolf spent the next two years at the Western Front. After studies at the University of Berlin he was resident pathologist at the Moabit Hospital in Berlin, carrying out studies on the production of atherosclerosis in animals by administration of cholesterol. While working at the University of Leipzig in the laboratory of Karl Thomas, he continued his earlier work on the role of cholesterol and in 1926 published a unique procedure for the synthesis of peptides.
In 1926 Schoenheimer became a docent (assistant professor) at the University of Freiburg, where he was on the staff of Ludwig Aschoff in the Pathological Institute. He spent the year 1930-31 in the United States as Douglas Smith Fellow in the department of surgery at the University of Chicago and was then made head of the department of pathological chemistry in Freiburg. Here he continued his work on sterols, investigating the occurrence and transformation of these compounds in both plants and animals, and establishing the fact that cholesterol undergoes continuous synthesis and degradation in mammals.
An edict of the new Nazi government in April 1933 ordered the dismissal of all Jewish faculty members in German universities. Professor Hans T. Clarke, chairman of the biochemistry department at Columbia University's College of Physicians and Surgeons, immediately offered Schoenheimer an assistant professorship, which he accepted. At Columbia, Schoenheimer continued his work on sterols and, in association with Warren M. Sperry, developed a procedure for determining traces of free and bound cholesterol in blood serum and plasma.
His most significant research began in 1934, after Harold Urey had successfully concentrated the heavy hydrogen isotope, deuterium. Seeking to use deuterium as an isotopic tracer, Schoenheimer, in conjunction with David Rittenberg, who had worked on deuterium in Urey's laboratory, developed methods of synthesizing isotopically labeled compounds (such as linseed oil hydrogenated with deuterium).
From Schoenheimer's experiments emerged the concept of a "metabolic pool, " with body tissues continually drawing chemical substances from it and releasing others to it.
Schoenheimer's career came to a sudden close on September 11, 1941, when he committed suicide by taking poison at his home in Yonkers, New York.
Rudolf suffered from manic depression all of his life. He was in state of severe mental depression associated with the successes of the German armies in Europe, with Nazi treatment of the Jews, and with personal problems - that was reason of his suicide.
On October 27, 1932, Schoenheimer married Salome Gluecksohn, a zoologist who had just completed her doctor of philosophy at Freiburg; she continued an active scientific career after the Schoenheimers came to the United States. They had no children.