Brilliancy ran in Garrod's family. Archibald was the fourth son of Sir Alfred Baring Garrod, a renowned physician who received his medical degree at the age of 23 and became a professor of medicine at University College, London by the time he was 32. He discovered the abnormal uric acid metabolism associated with gout. Garrod's father also successfully estimated the weight of crystals he obtained from a known quantity of blood, resulting in what Garrod called “the first quantitative biochemical investigation made on the living human body”. Garrod's two older brothers also had successful careers.