His mother, Bertha (née Melchior) Rosalie introduced Kalckar to a variety of French and German writers, including Gustave Flaubert, Marcel Proust, Johann von Goethe, and Heinrich Heine.

[5] In his autobiographical reflections, Kalckar spent little time on his early education and referred to high school biology experience as "somewhat static," except for "some extraordinary demonstrations in human physiology" by August Krogh.

Krogh, a physiologist and Professor at the University of Copenhagen, won the 1920 Nobel prize for his description of capillary blood flow and regulation, introduced the principles of human physiology to Danish high school students.

Kalckar completed his medical training at the University of Copenhagen in 1933, and then began research for his Ph.D. in Ejnar Lundsgaard's (1899–1968) physiology laboratory; that work established the foundation of a fundamental biochemical paradigm, i.e. "oxidative phosphorylation".

During this period, Lundsgaard was preoccupied as physiology department chair, consequently Fritz Albert Lipmann, who had recently fled Germany,[7] served as Kalckar's research mentor.

His key experiment demonstrated that in frog muscles where glycolysis had been inhibited with iodoacetate, muscular contraction continued for a short period using phosphocreatine as a source of energy.

[16] Upon completing his graduate studies, Kalckar received a Rockefeller research fellowship to spend a year at the California Institute of Technology (Caltech).

[17] Kalckar and his wife arrived in Pasadena in the spring of 1939 and rapidly became a part of the Caltech social and intellectual community, including Max Delbrück, Linus Pauling, and James and David Bonner.