He was born in Hildesheim, Germany, the son of Georg Krebs, also M.D., and his wife Alma. He went to school in Hildesheim and studied medicine at the University of Göttingen from 1918-1923. He gained his Ph.D. at the University of Hamburg in 1925, then studied chemistry in Berlin for one year, where he later became an assistant of Otto Warburg at the Kaiser Wilhelm Institute for Biology until 1930.
He then returned to medical work, which became forbidden under National Socialist rule in 1933. He was invited to Cambridge, where he studied biochemistry. He became professor of biochemistry at the University of Sheffield in 1945.
Krebs' area of interest was the intermediary metabolism. He discovered the urea cycle in 1932 and the citric acid cycle in 1937, which is still often called Krebs cycle. He was awarded the Nobel Prize in Physiology or Medicine in 1953.