An internist or Internal Medicine doctor is someone who specializes in diagnosing and treating illnesses, diseases, and health problems. Most internists are also primary care doctors and treat patients on a regular basis. They can diagnose and treat common illnesses or more serious problems. Most people see an internist regularly. Those with chronic illnesses may do so on a monthly or even weekly basis. Internists are the most common types of doctors.

Pathology is a medical subfield with a focus on the diagnosis of disease. Medical professionals who become pathologists often have background knowledge in several different areas of medicine, as this knowledge is helpful when it comes to diagnosis. Pathologists generally test for disease by analyzing tissue, body fluid, and cell samples. In this way, these doctors can diagnose problems caused by parasites, pathogens, and even non-infectious causes. This work can help other physicians make the proper treatment recommendations.