He was surgeon under General Johan Banér who led one of the armies of Queen Christina, the daughter of Gustavus Adolphus.
He was admitted to the Incorporation of Surgeons and Barbers of Edinburgh in 1640 in consideration of his "literature and qualifications" and on the payment of the sum of £200 Scots.
In his later years he was cared for by his son Alexander Pennycuik (or Pennecuick) (1652–1722) who had qualified and practised as a physician but found fame as a poet and naturalist.
[4] His estate of New Hall was thought to be the setting for 'The Gentle Shepherd', Allan Ramsay's celebrated pastoral poem.
His son, in a fond posthumous tribute, described his father as: "The oldest Aesculapian of his age… Who flattered not the rich nor scourged the poor From old forebears much worth he did inherit