He was awarded the Nobel Prize in Medicine in 1943 for joint work with Edward Doisy in discovering vitamin K and its role in human physiology.

They noticed that chicks fed only fat-depleted chow developed hemorrhages and started bleeding from tag sites.

The new vitamin received the letter K because the initial discoveries were reported in a German journal, in which it was designated as Koagulationsvitamin.

During his time as professor at the University of Copenhagen he spent some time working abroad, and in 1934 submitted a thesis entitled Nogle Undersøgelser over Sterinernes Biologiske Betydning (Some investigations on the biological significance of the sterines) to the University of Copenhagen, and received the degree of PhD in biochemistry.

[citation needed] Between 1942 and 1945 Dam was a senior research associate at the University of Rochester; it was during this period that he was awarded the 1943 Nobel Prize for Physiology or Medicine.