I wonder why you are trying to get a LOR from a theatre prof.
Are you a theatre major?
Have you known this professor for a long time and have a strong relationship?
If not, I would not ask a theatre prof for a LOR, and by the sound of it, I don't think your prof knows much about you and your goal of becoming a physician.
I would rather ask a faculty from social science or humanities department for non-science LOR.
But of course, it is your decision to make.
I don't think that your professor's department has anything to do with it. What matters is that they know you, and already have some sense of your interest in medicine before you apply.
Our pre-med committee sends three letters. The pre-med adviser told me that given the choice, he'd only send three from upper-division classes. I transferred here as a junior, and my strongest LOR (I think) comes from the chemistry department chair who taught me Honors chem and two semesters of orgo. I worked as a tutor, research coordinator, and presented at 11 conferences (two national ACS) under his supervision. He is attending my wedding, and knows me better than some of my friends.
I intentionally only asked for two more, so that his letter will be sent. One is from the department chair in my major, and the other is from someone who taught two of my honors classes. Others have offered, and I asked that they send personal LOR's on my behalf after I apply. When you're waiting to hear (or officially on the wait list), an email on your behalf can make a huge difference.
I think you need at least one LOR from a basic science professor and another from your department. The third can come from a research or EC adviser, or from anyone who can speak to your dedication to medicine. I don't think it matters who writes it, as long as they know you well enough to advocate for you.
If you don't have a pre-med committee, choose even more carefully, and keep those who are willing to advocate for you on reserve to send extra letters on your behalf.
