The three people, described by police as being in their 70s and 80s, were admitted Saturday to Hoag Hospital with nausea, dizziness and inability to stand unassisted.
The patients, residents of Huntington Beach and nearby Newport Beach, had been at a memorial service for a mutual friend where they had eaten brownies that contained marijuana, police said.
The patients said they had no idea the brownies contained so-called medical marijuana, the Huntington Beach Police Department said Sunday in posting on the department's Facebook page.
"It is important for the community to understand that marijuana is a drug, and like all other drugs and alcohol, it is important to understand the negative consequences it creates in our community," the police department said in the Facebook posting. "Calling it 'medical marijuana' does not make it any safer."