Tom Wilkinson chose not to do any research into the subject of transgenderism, as he felt that a mid-Western farmer wouldn't know anything about the subject either.
The John Deere tractor company refused to have anything to do with the film. This was not so much to do with the fact that the character of Roy is sexually conflicted; instead they took exception to a scene in which Roy gets roughed up at work. The company didn't want to be associated in any way with worker-related violence.
Tom Wilkinson had to endure regular close shaves with a barber to convey the impression that estrogen was working on his face. He also had to shave all the hair off his arms, legs and chest.
One of the films that Jane Anderson screened before working on "Normal" was Ingmar Bergman's "Scenes from a Marriage". She also screened "Tender Mercies" and "Country", one of star Jessica Lange's films.
Tom Wilkinson had a broken rib during the scene where Roy has a fight in his workplace. He had slipped and fallen in a restaurant the night before.