Math or statistics, if you like those subjects. Possible major-related career directions include data science, bioinformatics, high school math teaching, finance/actuarial. Computer science may also be a possibility, but that is more doable if at a college where it is not engineering-based (engineering-based CS majors tend to have extra requirements that make fitting pre-med courses into the schedule more difficult).
Yes, some business-type courses could be helpful if going into an area of medicine where you would run a private or small group practice.