After education at
Plymouth College and then from 1947 to 1951 at
Clifton College, Bristol, Cohen studied from 1951 to 1954 at
Trinity College, Cambridge, where he graduated with first class honours in the natural science tripos. He then studied medicine from 1954 to 1958 at the
London Hospital Medical College (LHMC). He graduated in 1958
MB BChir (Cantab.) and in 1966
M.D. (Cantab.). He qualified MRCP in 1960. In 1961 he married Barbara J. Boucher, who was also a medical student at LHMC. After junior appointments from 1958 to 1959 at the London Hospital, Robert Cohen was from 1959 to 1960 house physician at the
Royal Postgraduate Medical School, where he worked at the endocrine and metabolic unit under Russell Fraser. At LHMC, Cohen was in 1960–1965 lecturer in medicine, in 1967–1969 senior lecturer, in 1969–1974 reader in medicine, in 1974–1982 professor of metabolic medicine, and in 1982–1995 professor of medicine and director of the academic medical unit. After LHMC merged in 1995, he was in 1995–1999 professor of medicine and director of the academic medical unit at
Barts and The London School of Medicine and Dentistry. He retired as professor emeritus in 1999. Cohen was elected FRCP in 1971. He gave the
Bradshaw Lecture in 1981. He was an active member of numerous medical committees. He was elected FMedSci in 1998. He chaired from 1994 to 2001 the Imperial Cancer Research Fund and played a central role in its merger in 2002 with The Cancer Research Campaign to create
Cancer Research UK. He was appointed CBE in 1997. Upon his death Cohen was survived by his widow, a daughter, a son, and five grandsons. ==Lactic acidosis==