Kay's first book, This is Going to Hurt, based on diaries from his former career as a doctor, was published by Picador in September 2017[7] and became an instant Sunday Times bestseller.[8] The paperback edition was also an instant Sunday Times number one bestseller,[9] a position it held for well over a year[10] and selling over one million copies.[11] It was the book of the year in the UK's 2018 National Book Awards.[12]