The series was created by Glenn Gordon Caron and was initially based on the real-life experiences of self-described medium Allison DuBois, who claims to have worked with law enforcement agencies across the country.

The fictional setting 'Mariposa County' for Phoenix, Arizona is actually a play on Phoenix's real county, Maricopa County.

The show was produced by Glenn Gordon Caron's Picturemaker Productions in association with Kelsey Grammer's Grammnet Productions.

The series premiere drew 16.13 million viewers, competing against CSI: Miami's 18.17 million viewers in the same time slot.

Production on the fourth season was disrupted by the 2007 Writers Guild of America strike, which forced the show to halt filming and resulted in only nine episodes for that season.

After NBC canceled the show in May 2009 over failed episode-count negotiations, CBS—whose production arm made the series—renewed it within 24 hours for a full 22-episode sixth season.

For its sixth season, Medium was scheduled between fellow CBS in-house productions Ghost Whisperer and Numb3rs on Friday nights, and the two supernatural-themed shows often traded off as the night's most-watched program.

In May 2010, CBS renewed Medium for a seventh season while canceling seven other series including Ghost Whisperer, a decision analysts attributed to CBS fully owning Medium's production rights while Ghost Whisperer was split with ABC.