Hans Christian Geelmuyden (1861-1945) was amanuensis (assistant professor) at the Institute of Physiology, University of Oslo from 1889 to 1931. In 1897 he was awarded the degree "Doctor of Medicine" for his thesis "Om aceton som stofvexelprodukt" (On acetone as a metabolic product). The Nobel laureate Feodor Lynen referred to this thesis, which was also published in German, stating that Geelmuyden was the first to establish that ketone bodies are formed from fatty acids. Geelmuyden also established that acetone is metabolized in rabbits and dogs. Geelmuyden was a prolific writer on fat metabolism and diabetes and wrote a series of extensive reviews on these topics in Ergebnisse der Physiologie. Geelmuyden was active in the treatment of diabetic patients.