Competitive applicants to medical schools are well rounded and have pursued a wide range of experiences to develop not only their scientific, thinking, and reasoning skills, but also interpersonal and intrapersonal competencies. Most medical schools like to see some job shadowing or experience working directly with physicians so you have some idea what the doctor-patient relationship is like from the physician’s perspective, and some experience working with patients so you know you are comfortable being around sick people. But there is no set number of hours required - it’s more about quality than quantity of experience.
Volunteering and community service, whether or not it is in a healthcare setting, demonstrates your commitment to serving others, as you will as a future physician.
Research experience helps you to learn the problem-solving skills needed to think like a physician, and develop an understanding and appreciation for the scientific and medical research that will be the basis for modern medical practice.
Becoming a leader in a student organization, job, etc. gives you experience working with teams, communicating, and working together to share responsibility for accomplishing shared goals. Consider joining organizations such as BU Med or Alpha Epsilon Delta honor society, and working your way toward an executive board or other leadership role.