In May 1838 James John Louis Donnet of Gibraltar was included in the list of gentlemen to whom the Court of Examiners of the Apothecaries' Hall granted certificates of qualifications.
Assistant-Surgeon James Donnet of the Greenwich Hospital was appointed to the rank of surgeon in December 1845
Surgeon Superintendent Convict Ship
He was appointed Surgeon Superintendent of the William Jardine convict ship in 1852 . The William Jardine departed Plymouth 3 May 1852 and arrived in Western Australia 1st August 1852.
In 1867 he was promoted to the rank of deputy inspector general of Hospitals and Fleets in her majesty's fleet. 
He was appointed Deputy Inspector-General of Hospitals and Fleets in 1870 
In 1875 he was promoted to the rank of Inspector General of Hospitals and Fleets. 
On 7 February 1893 he was appointed to be Hon. Physician to Her Majesty .
In the 1897 Diamond Jubilee Honours he was appointed a Knight Commander of the Order of the Bath.
In the 1901 Census James Donnet gave his age as 85 years and birth place Gibraltar. He resided at 5 Park Road Bognor, Sussex with his wife Eliza age 70. They employed two servants.
He died on 11 January 1905 in Sussex.
His Obituary was published in the London Times on 12 January 1905......
Sir James John Louis Donnet K.C.B., Inspector-General of Fleets and Hospitals R.N., retired, died yesterday at the residence of his daughter at Bognor, in his 89th year. Sir James Donnet was the son of Surgeon Henry Donnet R.N., by his marriage with Elizabeth, daughter of Mr. John Moore of Dublin, Philadelphia, and Gibraltar. He was educated in Paris, Edinburgh, and London and joined the Navy as an assistant surgeon in 1840. In this rank he was present in the Vesuvius at the operations on the coast of Syria and at the siege and fall of St. Jean D'Acre, and he had charge of the R.M. Hospital at Acre after the fall of that place. Four years later he acted as secretary to the diplomatic mission sent by the British government to the Sultan of Morocco, and in 1848 having been promoted surgeon in 1845, he was in medical charge at the successful capture and destruction of the town of Ngunduvan in Viti Levu, Fiji. His next notable service was with the Arctic expedition of 1850 - 51, in the Assistance, when the first footprints of Franklin were discovered, and then, three years later, as senior medical officer of the flagship President, during the Russian war.
He was promoted to the rank of deputy inspector general in 1867 and to that of inspector general in 1875 and in those ranks before his before his retirement in 1876 he filled many important posts in or connected with the medical service of the Navy.
He was in administrative and executive charge of Port Royal Hospital, Jamaica during the epidemics of yellow fever of 1867 and 1869; principal officer in charge of the medical wards of the Royal Naval Hospital, Haslar, during the epidemics of smallpox and enteric fever, and cases of fever and dysentery after the Ashanti war of 1873-4 and in administrative and executive charge of the Royal Naval Hospital, Malta in 1874. He was a member of the committee appointed in 1876 to choose a site for the Naval Cadets College, and also of that formed to inquire into the causes of the outbreak of scurvy in the Arctic expedition under Sir George Nares. At the time of his death Sir James Donnet was an honorary physician to the King. Sir James married in 1852 Eliza (who died in 1903), daughter of Mr. James Meyer.