Internists are uniquely qualified to provide primary health care and follow patients through adulthood. There are some internists who work as hospitalists, providing primary care to patients in hospitals; others provide only outpatient care. It is also possible for general internists to practice in long-term care facilities and rehabilitation centers.   Heart disease, hypertension, diabetes, obesity, and lung disease are just some of the conditions studied, diagnosed, and treated by internal medicine. Specialists in internal medicine often treat people with complex, chronic, and multisystem diseases.   Internists may work with other medical specialists or consult on patients referred by other specialists depending on their subspecialties. Depending on a patient's condition, overall health, and wellness goals, internal medicine specialists perform tests, procedures, or surgery. Medical procedures can be performed by internists, nurses, and other providers according to their specialty, diagnosis, and treatment. In order to minimize patient discomfort, optimize outcomes, and reduce side effects, healthcare providers need experience, skill, and often additional training and medical credentials.