Whether medical assistants work in a large hospital or a small doctor's office, their job duties remain the same. As a medical assistant, you may greet patients when they first arrive, ensure patient forms are filled out correctly, answer phone calls, and schedule appointments. Some also handle billing and insurance claims. In the exam rooms, medical assistants may take vital signs, administer medication or vaccinations, describe procedures, change wound dressings, document results from patient sample testing, submit prescriptions, and prepare the beds for the next patient. In a hospital, medical assistants tend to the needs of the staff and patients in their particular unit.