I saw this movie on television once…I think it may have been on Disney Channel, it was a teen horror comedy where one of the characters has a condition (think clinical lycanthropy or Renfield’s) where he starts to feel like he’s turning into a zombie, it’s similar to movies like Teen Witch or Teen Wolf.
Disney – Zombies (2018)?
https://en.wikipedia.org/wiki/Zombies_(2018_film)
I don’t think that’s it, it came out before zombies and it was basically more like George Romero’s Martin but as a movie for kids/teenagers, I remember seeing it on Disney Channel in the early 2000’s, it possibly could have been an episode of one of the sitcoms too (maybe a halloween episode)