Internal medicine physicians, or internists, specialize in the diagnosis, treatment, and care of complex illnesses of adults. They handle the ongoing care of chronic illnesses, and in caring for patients with more than one disease. Internists also specialize in health promotion and disease prevention.

Pulmonary medicine is the subspecialty of internal medicine that focuses on the diagnosis and management of disorders of the respiratory system, including the lungs, upper airways, thoracic cavity, and chest wall.

Geriatrics specializes in the diagnosis, treatment, and prevention of disease and disability in older adults. Geriatric physicians are primary care doctors who are specially trained in the aging process.

Sleep medicine is a medical specialty devoted to the diagnosis and therapy of sleep disturbances and disorders.

Family medicine, formerly family practice, is a medical specialty devoted to comprehensive health care for people of all ages. The specialist is named a family physician or family doctor.