If you are a graduate or post-bac student, ask your current professors to write LORs. If you have been working full-time with no classes for several years, you may be allowed to substitute employment letters. However, some schools may require refresher coursework and letters from those professors. Other potential sources of LORs for non-trads include volunteer coordinators, physicians whom you have shadowed, or researchers for whom you have volunteered. Contact the individual schools for more information about appropriate sources of LORs.