"Vitamin D" is the sixth episode of the American television series Glee. The episode premiered on the Fox network on October 7, 2009. It was written by series creator Ryan Murphy and directed by Elodie Keene. In the episode, glee club director Will Schuester pits the male and female club members against each other for a mash-up competition. Will's wife Terri takes a job as the school nurse to stop him becoming closer to guidance counsellor Emma Pillsbury, and starts giving the students performance-enhancing pseudoephedrine tablets.

William Michael Schuester, often referred to as Mr. Schue, is a fictional teacher character and one of the two main protagonists from the Fox musical comedy-drama series Glee, alongside his student Rachel Berry. He appeared in Glee from its pilot episode, first broadcast on May 19, 2009. Will was portrayed by Matthew Morrison, and was developed by Glee creators Ryan Murphy, Brad Falchuk, and Ian Brennan. He is a Spanish teacher at the fictional William McKinley High School and the director of the show's titular glee club in Lima Ohio, where the show is set. He ultimately becomes the school's principal. His storylines have seen him revive the school's failing glee club, leave his wife Terri, win the love of school guidance counselor Emma Pillsbury, and marry her.