Archibald Garrod was the son of the physician, Alfred Baring Garrod, who diagnosed and studied rheumatoid arthritis. Although his father initially intended for Archibald to study business, his teachers recognized and encouraged him to go into the field of science and medicine. Garrod studied medicine at Oxford University and became a physician.

Garrod was studying the human disorder alkaptonuria. He collected family history information (as well as urine) from his patients. Based on discussions with Mendel advocate William Bateson, Garrod deduced that alkaptonuria is a recessive disorder. In 1902, Garrod published a book called The Incidence of Alkaptonuria: a Study in Chemical Individuality. This is the first published account of a case of recessive inheritance in humans.

Garrod was also the first to propose the idea that diseases were "inborn errors of metabolism." He believed that diseases were the result of missing or false steps in the body's chemical pathways. In 1923, his studies on alkaptonuria, cystinuria, pentosuria, and albinism were published as a book: Inborn Errors of Metabolism. Garrod attributed a biochemical role to genes, and laid the groundwork for the next wave of discovery -- the molecular basis of inheritance.

Garrod was more of a scientist than a physician. His bedside manner was said to be limited to his interest in his patients' urine samples. Garrod did have a strong sense of duty and served as a colonel in Malta in World War I. He was knighted in 1918. The death of two of his sons in the war and of a third son (his last) in the post-war influenza epidemic was a sad blow in the later years of Garrod's life.