Yes, a letterhead usually includes the logo of the institution, some sort of contact (address, email, etc). For example, if you ask a professor from the English department, the letter should consist the logo of the university, the department's name and maybe its phone number.
Almost all letter writers will include an official letterhead, but it's a virtue to remind them. Especially professors and healthcare business people. They know a LOR without a letterhead isn't going to be perceived as much.