B Positive

• Thomas Middleditch as Drew,[5] a divorced father and therapist in need of a kidney transplant and a social life.
• Annaleigh Ashford as Gina,[5] a former acquaintance of Drew's from high school who works as a bus driver for a senior center. She becomes Drew's kidney donor as her blood is an incredibly rare match for his.
• Kether Donohue as Gabby,[5] a party girl and Gina's best friend who juggles multiple jobs.
• Sara Rue as Julia,[5] Drew's ex-wife, a realtor who aspires to climb the social ladder; her frustrations with trying to get Drew to embrace her interests more led to her having an affair that resulted in their split.
• Izzy G as Maddie, Drew and Julia's daughter.
• Terrence Terrell as Eli, a retired football player with an upbeat personality whom Drew meets during dialysis treatment.

• Linda Lavin as Norma, one of the senior citizens that Gina works with at a local retirement home. She has a maternal, nurturing relationship with Gina.
• Briga Heelan as Samantha, an uptight, intense millennial in Drew's dialysis group who does not suffer fools. She is angry about her illness and often takes it out on those around her. She is trying not to let dialysis get in the way of her climbing the corporate ladder.
• David Anthony Higgins as Jerry, a dentist who has been in dialysis for over a year, convinced he’ll never find a donor. He always sees the glass half-empty.
• Darryl Stephens as Gideon, an empathetic nurse who works at the dialysis center. He cares deeply about the people to whom he gives treatment, often getting involved in their personal lives
• Bernie Kopell as Mr. Knudsen, one of the senior citizens at the retirement home where Gina works.

• Jason Kravits as Dr. Baskin, Drew's nephrologist.
• Tim Bagley as the minister of the marriage where Drew and Gina meet.
• Jessica Tuck as Dr. Goodson
• Darien Sills-Evans as Benny, a philosophy professor at Fordham; he is a mix of emotions—excited, nervous and angry—about finding himself single again.

The series was among the 14 pilots ordered by CBS in February 2020 and was fast tracked to series the following March, as the pilot had already been completed before production at Warner Bros. Television was closed because of the COVID-19 pandemic.[15] The pilot was the only pilot completed for the 2020–21 television season for any of the broadcast networks in advance of the upfronts. On May 8, 2020, CBS picked up the series,[1] and CTV followed soon after, picking up the series on June 23, 2020.[16] On October 26, 2020, Jim Patterson joined the series as an executive producer and co-showrunner.[17] The series premiered on November 5, 2020.[3][18] On December 21, 2020, CBS gave the series a five-episode back order, making the total number of episodes ordered to 18.[19]

On February 19, 2020, it was announced that Annaleigh Ashford had been cast in the pilot.[20] On March 2, 2020, it was announced that Kether Donohue and Sara Rue had joined the cast.[21] The following day, it was announced that Thomas Middleditch had joined the cast in the lead role.[22] Alongside the series picked up announcement, it was reported that Kamryn Kunody was cast in a starring role.[1][23] On August 11, 2020, Maggie Elizabeth Jones joined the cast in a recasting, replacing Kunody.[24] On September 25, 2020, Terrence Terrell was cast as a series regular.[25] On October 12, 2020, Izzy G was cast to replace Jones in a second recasting while Linda Lavin, Briga Heelan, Darryl Stephens, Bernie Kopell, and David Anthony Higgins were cast in recurring roles and Darien Sills-Evans was cast to guest star.[26]

On Rotten Tomatoes, the series holds an approval rating of 87% with an average rating of 6.12/10, based on 15 reviews. The website's critical consensus states, "B Positive's familiar sitcom trappings are elevated by its charming cast—especially the weird and winsome comedic stylings of Tony winner Annaleigh Ashford."[27] On Metacritic, it has a weighted average score of 62 out of 100, based on 14 critics, indicating "generally favorable reviews".[28]