John Williams was last seen at his care home in the 300 Block of Juana Avenue in San Leandro at 11:30 a.m. Tuesday.
Williams is described as a black man standing 5 feet 7 inches tall and weighing about 160 pounds. He has gray and black hair and brown eyes, police said.
Williams was last seen wearing a brown beanie, a black jacket and black pants.
He left his home to cash a check in Oakland, but did not return in time to take his daily medications, police said.
Williams is considered to be at-risk due to his medical condition, police said.
According to police, Williams primarily used AC Transit to get around the area. He moves very slowly and walks with a cane. He also has a distinctive hunched over walk.
Williams was previously reported missing last week and was found by a San Leandro police officer in the 2200 block of Bancroft Avenue in San Leandro.
Anyone who sees Williams is urged to contact their local police department immediately.
