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Holmes, accused of gunning down 12 people and wounding 58 more at a screening of Batman movie "The Dark Knight Rises" in July, had been due in court Thursday for a routine hearing.
But the court date has been postponed until December 10, after Holmes's lawyers requested an emergency court session following Tuesday's incident, said Colorado state courts spokesman Robert McCallum.
The defense lawyer told the judge that there was an "incident that required Mr Holmes to go to the hospital yesterday, and it would not be something that would resolve itself by tomorrow," McCallum told AFP.
The Denver Post cited sources as saying that Holmes injured himself at the Arapahoe County jail, where he has been detained since shortly after the July massacre.
"In the middle of the day yesterday, we received information for the situation (that) involved a trip to the hospital," the newspaper cited attorney Tamara Brady as telling the court.
"It's not as simple as a migraine."
Holmes, who has previously appeared in court looking bewildered with bright orange hair, has been held in solitary confinement since the massacre, one of the deadliest shootings in recent US history.
He could face the death penalty if convicted, although Colorado has only executed one person since capital punishment was reinstated in the western US state in 1976.