During his final years at Harvard, Starkey became increasingly occupied with the practice of medicine. He was a devoted follower of the Flemish iatrochemist Jan Baptist van Helmont, and had been tutored in the practical applications of metallurgy. His medical practice appears to have been highly successful, which included iatrochemistry. Despite his flourishing practice, Starkey decided England could provide better access to the tools required by an alchemist, which prompted him to sail for London with his wife in November 1650.