David Chan suffers from diabetes and needs insulin as soon as possible, according to police. Chan also has trouble walking and is described as senile, police said.
Chan is about 5 feet 1 inch tall and weighs about 100 pounds, according to police. He was last seen wearing gold framed glasses, a neon green jacket, grey sweater, black pants, a black fanny pack and white shoes, police said.
A photograph of Chan may be viewed at http://www.sfgov.org/site/police--index.asp.
Anyone with information about his whereabouts is asked to contact the San Francisco Police Department's Missing Persons Unit at (415) 558-5508 or police operations at (415) 553-1071.