Krebs was born in
Lansing, Iowa, the third child of William Carl Krebs, a
Presbyterian minister, and Louise Helen (Stegeman) Krebs. The family moved frequently due to the nature of his father's work, though they settled in
Greenville, Illinois when Krebs was six and remained there until his father's unexpected death in 1933. Louise Krebs decided to move her family to
Urbana, Illinois, where Krebs's elder brothers were attending the
University of Illinois Urbana–Champaign. Krebs attended
Urbana High School, and enrolled at the University of Illinois Urbana–Champaign in 1936. In his fourth year of study Krebs had decided to either pursue a higher degree in
organic chemistry or study medicine. Receiving a scholarship to attend
Washington University School of Medicine in
St. Louis, he chose the latter. The School of Medicine afforded Krebs the opportunity to train as a physician as well as to gain experience in medical research. Following graduation in 1943, he undertook an 18-month residency at
Barnes Hospital in St. Louis and then went on active duty as a medical officer in the
Navy. Krebs was discharged from the Navy in 1946 and was unable to immediately return to hospital work; he was advised to study basic science instead. He chose to study
biochemistry and was postdoctoral fellow to
Carl and
Gerty Cori, working on the interaction of
protamine with rabbit muscle
phosphorylase. At the completion of his two years' study, Krebs decided to continue his career as a biochemist. ==Research work==