1827 Qualified LRCS Edinburgh. His father had served at Waterloo with the 13th Light Dragoons and afterwards with the 5th Dragoon Guards.
1828 Received his MD from the University of Glasgow.
8 May 1828 Appointed Hospital Assistant.
29 July 1830 Became Assistant Surgeon. The Royal Warrant of 1830 abolished the rank of Hospital Assistant and replaced it with that of Staff Assistant Surgeon.
19 Nov 1830 Promoted Assistant Surgeon 53rd (Shropshire) Regiment of Foot vice Assistant Surgeon James Connell who was appointed to 3rd Light Dragoons on 19 Nov 1830.
Malta Aug 1834 Absent without leave since 20 June 1834, when he was supposed to have joined the Regimental Depôt.
28 July 1840 Appointed Staff Assistant Surgeon vice Staff Assistant Surgeon John Summers who replaced Assistant Surgeon James Davidson 21st Regiment. Davidson in his turn became surgeon 50th Foot, on the death of Surgeon John Reid in New South Wales, on 12 January 1840.
Served at York.
15 Jan 1841 Assistant Surgeon 53rd Foot vice Assistant Surgeon Edward Scott Docker, who was appointed to 54th Foot on the death of Assistant Surgeon Richard Houston Everard at Dover on 24 December 1840. The subsequent vacancy on the staff was filled by Gentleman Philip Whiteside Maclagan MD.
10 Aug 1842 Promoted Surgeon 53rd (Shropshire) Regiment of Foot.
1845–1846 Served in the Sutlej Campaign with the 53rd Regiment. He took part in the actions of Buddiwal, Aliwal, and Sobraon for which he received a medal with clasps.
11 Oct 1847 Exchanged with Surgeon Nelson Dartnell 4th, or King's Own Regiment, who moved to 53rd Foot.
5 Nov 1852 Promoted Staff Surgeon of the 1st Class vice William Dobson who retired upon half-pay. The vacancy in 4th Foot was filled by Surgeon Richard Francis Valpy De Lisle.
1852–53 Served in York and the West Indies.
1854 On duty in Bermuda.
Sep 1855 Served in the Crimean War. Was present at the taking of the quarries on 7 June, and the assault of Sebastopol on 18 June. At the time of the final assault of Sebastopol, on 8 September, Dr Logan was PMO of the Highland Division.
21 Dec 1855 Promoted Deputy Inspector General.
1856–57 On duty at Shorncliffe.
2 Mar 1858 Awarded the Imperial Order of the Medjidie (5th Class) by the Sultan for his distinguished services before the enemy during the war against Russia.
1858–1874 On duty in London. In 1858, he married Christiana Mary Ruth Wilford, only daughter of Colonel E C Wilford of the Royal Staff Corps and School of Musketry.
8 Apr 1859 Promoted Inspector General. Became Head of the Sanitary Branch Medical Department of the War Office.
16 Aug 1859 Honorary Physician to the Queen.
July 1865 Made a Companion of the Order of the Bath.
30 Mar 1867 Appointed Director General Army Medical Department. The unification system of administration of the Army Medical Department was introduced under the directorship. Under the system, regimental surgeons were removed from the control of commanding officers and became part of the Army Medical department. Sir Galbraith Logan faced great opposition in military and medical circles against his scheme and became the subject of much personal attacks in the press. The Unification System became more effective under his successor Surgeon General Sir William M Muir who took control of the Army Medical Department in April 1874.
June 1869 Became a Knight Commander of the Order of the Bath.
1 Apr 1874 Retired to half-pay having completed 46 years service on full pay. He was asked to represent the Universities of Edinburgh and St Andrews in Parliament on the Conservative side, but advancing age obliged him to decline. He was a Fellow of the Royal Geographical Society and was on the Patriotic Fund Commission.
May 1883 On the death of Surgeon J. Wyer, the Good Service Pension was awarded to Sir Thomas Galbraith Logan KCB, Honorary Physician to the Queen and formerly Director of the Army Medical Department, for distinguished and meritorious service. The reward was one of the fourteen good service pensions allotted to the Army Medical Department to be conferred on meritorious officers, subject to the approval and recommendation of the Director General, who at the time was Director-General Thomas Crawford.
10 June 1896 Died at 5 Cambridge Terrace, Hyde Park, London. He was survived by his widow Dame Christiana Mary Ruth Logan.