Bailiffs cleared the courtroom and paramedics were seen going inside a few minutes later.
Defense attorney Matthew Fletcher said Knight was unconscious when the lawyer left the courtroom and an update on his condition was not immediately available.
Fletcher said his client, who is diabetic and has a blood clot, previously told him that he hadn't received any medication since yesterday.
Fletcher said Knight hit his head on a chair when he fell after the bail hearing.
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The attorney said Knight was being kept in solitary confinement without proper access to medication.
"He's being treated worse than Charles Manson," Fletcher said.
The collapse marked the fourth time that Knight has been taken by ambulance from a courthouse since he was charged with killing Terry Carter, 55, in early February.
Los Angeles Superior Court Judge Ronald S Coen set bail on Friday at USD 25 million for Knight, who is accused of running down and killing Carter with his truck.
"He escalated his behavior and committed murder," Barnes told the judge.
Fletcher argued that Knight's bail should be set at USD 2 million, but Coen said the higher amount was warranted.
The attorney said before the hearing that his client likely could not post bail if it was set at USD 25 million.
Knight, the 49-year-old co-founder of Death Row Records, has pleaded not guilty to murder, attempted murder and hit-and-run charges.