Most BS/MD programs want a student to apply for regular undergrad and then, if deemed eligible, to apply for BS/MD program. Undergrad applications require recommendation letters and so do the subsequent supplementary BS/MD applications. Can the teacher who gave recommendation letter for undergrad app (through Common App) write the recommendation for the subsequent BS/MD application? Or, should they be different?
Your statement is not entirely true. Your common App LORs can be used for BSMD. Please include science/math teacher’s recommendations in your common app. One can select which LORs goes to a program in common app when submitting the application. Sometimes one may need a different set of LORs for BSMD. Yes, the letter writers can be same.