Kirkland was born at Ashbourne, Derbyshire, the son of Thomas Kirkland, an attorney, and his father's second wife, Mary Allsop.
After a grammar school education he was apprenticed to a surgeon in Loughborough.
In January 1760 he became involved in the murder case around Laurence Shirley, 4th Earl Ferrers: he was called in to attend the steward of Lord Ferrers after he had been shot by his master.
[2] Kirkland, detained to dinner with the disturbed Earl, left the house covertly, brought a magistrate with armed men, and removed the wounded steward, Johnson, who soon died.
He subsequently became a member of the Royal Medical Societies of Edinburgh and London.