No requirement says you must have a medical job but working in healthcare has benefits specific to your career goals that non-medical jobs do not. That said, medical schools do like to see diverse candidates with diverse skill sets and backgrounds.
If you take a non-medical job, be sure to fill in the gaps with relevant medical experiences. This can be done with volunteering, medical shadowing, clinical experience, and research. Also, be sure to talk about the transferable skills you developed at your non-medical job. For example, interpersonal skills, leadership, and critical thinking are all essential core competencies for entering medical students.