During his early medical training he served as vice-president of the Glasgow Medico-Chirurgical Society and won the Cullen Medal for materia medica and the Hunter medals for midwifery and clinical surgery.

[3] He began his medical training at the University of Glasgow and obtained a BSc in pure science as well as his MB and Ch.B (Commended).

[3] Underwood worked as resident physician at the Western Infirmary, Glasgow, and in 1926 earned a diploma in public health.

[2][3] He also wrote the 460-page Annual Report on the Health Services for the Year 1937, in the County Borough of West Ham, while simultaneously publishing on history of medicine including his take on the 1832 pamphlet Cholera Morbus, Precautions, Preventives, and Remedies.

[2] Between 1935 and 1962 he published history of medicine–related articles regularly in the Royal Society of Medicine Proceedings.

[4] In 1962, he published a revised edition of Charles Singer's A Short History of Medicine.

[1] In 1965, Underwood became a fellow of the Royal College of Physicians,[2] and in 1970 he received an honorary DLitt from the University of Glasgow.