Bloch was born in Neisse (Nysa), in the German Empire's Prussian Province of Silesia. He was the second child of middle-class parents Hedwig (Striemer) and Frederich D. "Fritz" Bloch. From 1930 to 1934, he studied chemistry at the Technical University of Munich. In 1934, due to the Nazi persecutions of Jews, he fled to the Schweizerische Forschungsinstitut in Davos, Switzerland, before moving to the United States in 1936. Later he was appointed to the department of biological chemistry at Yale Medical School.