"undergraduate student in preparation for medical school," 1934, from premedical. From 1941 as "a major in preparation for medical training." As an adjective from 1936.
Examples from the Web for pre-med
Nor is this a diet of austerity or one that requires the tenacity of a pre-med student.The Diet That Shrinks Smarty Pants
April 24, 2009
Been hearing about it ever since I was a pre-med student at ucla.Disturbing Sun
Robert Shirley Richardson
I graduated—I went to undergraduate school at the University of Arkansas from 1950 to 1953, in pre-med.Warren Commission (6 of 26): Hearings Vol. VI (of 15)
The President's Commission on the Assassination of President Kennedy