William H. Andrews qualified at the Royal Veterinary College in London (BSc and MRCVS) in 1908 and joined Sir Arnold Theiler's* research team at the Veterinary Research Institute, Onderstepoort in 1910. That same year he became a member of the Transvaal Veterinary Medical Association. His early work at Onderstepoort was reported in "Some experiments on the drug treatment of Trypanosomiasis" in the Second Report of the Director of Veterinary Research (1912, pp. 362-383) and in papers on dysentery in lambs (1912) and the symptomatology and pathology of snake-bite in domestic animals (1913), both in the Veterinary Record. With regard to the latter topic he had already contributed a paper, "On the effects of the bite of certain opisthoglyphous snakes", to the Report of the South African Association for the Advancement of Science in 1912 (pp. 269-278).
During World War I (1914-1918) Andrews served in the South West Africa Campaign as a captain in the South African Veterinary Corps and in 1918 took charge of the Allerton Veterinary Laboratory in Natal. While there he studied "Staggers" or "Pushing Disease" in cattle and identified poisoning with Matricaria nigellaefolia as its cause. This research earned him a DSc degree from the University of London in 1922. He served on the first council of the South African Veterinary Medical Association in 1920/1. In 1916 he became a foundation member of the South African Biological Society.
In 1921 Andrews was appointed Professor of Physiology at the newly established Veterinary Faculty of the University of Pretoria at Onderstepoort. As co-author with H.H. Green* he published a paper on "The toxic principles of Adansonia digitata" in the South African Journal of Science (1923, Vol. 22, pp. 273-274). He left South Africa in 1924 for England, where he worked in McFadyean's laboratory at the Royal Veterinary College in London until his appointment as Director of the Weybridge Veterinary Laboratories in 1927, succeeding Sir Stewart Stockman*. In 1929 he attended the Pan African Conference in Pretoria as a United Kingdom representative. After his retirement in 1947 he returned to South Africa as a guest worker at Onderstepoort until his death in 1953. He was survived by his wife Doris, a son and a daughter.