Andrew Doig was a consultant physician at the Royal Infirmary of Edinburgh. He was born in Edinburgh. His father, James Doig, was a compositor in the print trade; his mother, Margaret Campbell Doig née Wilson, was the daughter of a groom. He had two younger twin brothers, Wilson Campbell and James. Doig was educated at Craiglockhart Primary School and then Boroughmuir High School in Edinburgh. He studied medicine at Edinburgh University and qualified in 1952 with the William Leslie prize.

He was a house physician and house surgeon at the Royal Infirmary, Edinburgh and then became a senior house physician at the Victoria Hospital, Burnley, Lancashire. From 1955 to 1957 he was an assistant lecturer at the University of Edinburgh. From 1957 to 1963 he was a registrar and then a senior registrar on the professorial medical unit at the Royal Infirmary, Edinburgh, including a year as a United States Public Health Service research fellow in the department of medicine, University of Illinois, Chicago.

In 1963, he was appointed as a consultant physician at the Royal Infirmary and a senior lecturer in medicine at the University of Edinburgh. He wrote papers on renal disease and hypertension.

He enjoyed swimming, gardening, fishing, tennis and hillwalking. In 1953, he married Anne Bisset Duthie. They had a son and a daughter, Jenny.

RCP editor