American College of Physicians Collection

Internal medicine physicians are specialists who apply scientific knowledge and clinical expertise to the diagnosis, treatment, and compassionate care of adults across the spectrum from health to complex illness.

What’s an “Internist”?

Internists are physicians specializing in internal medicine, a discipline focused on the care of adults emphasizing use of the best medical science available in caring for patients in the context of thoughtful, meaningful doctor-patient relationships as exemplified by the life and work of Sir William Osler, the “father” of internal medicine in the United States.

At least three of their seven or more years of medical school and postgraduate training are dedicated to learning how to prevent, diagnose, and treat diseases that affect adults. This basic training qualifies them to practice internal medicine, and you may see these physicians referred to by several terms, including “internists” or “doctors of internal medicine.” But don’t mistake them with “interns,” who are doctors in their first year of residency training. Internists are sometimes referred to as the “doctor’s doctor,” because they are often called upon to act as consultants to other physicians to help solve puzzling diagnostic problems.

General Internal Medicine

Many internists enter into practice following completion of their basic internal medicine training.  These physicians practice “general internal medicine” and are commonly referred to as “general internists.” General internists are equipped to handle the broad and comprehensive spectrum of illnesses that affect adults, and are recognized as experts in diagnosis, in treatment of chronic illness, and in health promotion and disease prevention—they are not limited to one type of medical problem or organ system. General internists are equipped to deal with whatever problem a patient brings—no matter how common or rare, or how simple or complex. They are specially trained to solve puzzling diagnostic problems and can handle severe chronic illnesses and situations where several different illnesses may strike at the same time.

General internists may practice in a variety of settings. Their training uniquely qualifies them to practice primary care and follow patients over the duration of their adult lives and establish long and rewarding personal relationships with their patients. Although internists may act as primary care physicians, they are not “general practitioners,” or “family physicians,” whose training is not solely concentrated on adults and may include pediatrics, obstetrics, and surgery (Learn more about the difference between general internal medicine and family medicine). Some general internists may focus their practice on caring for patients in the hospital setting, and may be referred to as “hospitalists;” the majority of hospitalists in the US are general internists. Still other general internists will combine these facets of care and provide both outpatient and inpatient care for their patients.  And other general internists may practice in unique settings such as rehabilitation centers and long-term care facilities, among other clinical settings.

Hear from ACP’s CEO about why adults should choose an internist. 

Internal Medicine Subspecialties

Some internists choose to take additional training to “subspecialize” in a more focused area of internal medicine. Subspecialty training (often called a “fellowship”) usually requires an additional one to three years beyond the basic three year internal medicine residency.  Although physicians who have completed additional training in a particular area of internal medicine are frequently referred to by their area of subspecialty focus (for example, those who subspecialize in diseases of the heart are usually called “cardiologists”), all share the same basic internal medicine training and like general internists are also considered “internists.” The training an internist receives to subspecialize in a particular medical area is both broad and deep, and qualifies them to manage very complex medical issues and in many cases perform advanced clinical procedures.