I am assuming that by "premed letter" you mean a pre-medical committee letter.
LORs for nontrads can be hard, because you've lost touch with profs you worked with. However, LORs are a super-critical part of your application. You need to have strong and personal references. The old "Bob showed up to class and was 42nd out of 525 students" stuff is pretty pedestrian.
My school's premed office assigned me an MD advisor who was also an alum. (They do not have a committee.) Even better, he also took some time to do other things after undergrad. This advisor just advised on medicine, not on the application process.
My advisor really helped me with understanding medicine, and he also helped my application. He wrote me a cover LOR that gave an overview of my other LORs, plus his own personal insights. (At least, that's what the office asked him to write; I obviously never read it.)