MB ChB Manch 1943; DCH 1944; FRCP 1971.
Mackay was born on 29 October 1919 in Chorlton-cum-Hardy, Manchester, the son of Alexander Morrison Mackay, a general practitioner. He was educated at Altrincham Grammar School and the University of Manchester, where he won a number of prizes. Mackay held resident appointments at MRI, Royal Manchester Children's Hospital, Stepping-Hill Hospital Stockport and the Children's Hospital, Birmingham. In 1946 he was appointed registrar to the Duchess of York Hospital for Babies, Manchester, and the following year became senior registrar.
In 1948 Mackay became visiting paediatrician to Stepping Hill Hospital and Hope Hospital Salford, and assistant visiting physician to the Duchess of York Hospital. From 1950 he was consultant to Hope Hospital and from 1965 to Royal Manchester Children's Hospital. Mackay also lecturer in child health at the University of Manchester and at Salford University. Mackay was a member of MMS from 1943 and was president of the paediatric section in 1980. He was a foundation member of Manchester Paediatric Club and was president in 1964, and was a founding fellow of the Royal College of Paediatrics and Child Health and the Community Paediatric Group of the British Paediatric Association. Mackay retired from hospital paediatrics in 1980 and worked part time in Community Child Health. He became doctor to Manchester Grammar School in 1982.