An internist is a medical doctor who specializes in the care of adults. People might choose an internist as their primary doctor for regular checkups and for treating illness.

Internists can further specialize in areas such as:

• Adolescent medicine (conditions and diseases common to teenagers).
• Allergy, or immunology (immune system diseases).
• Cardiology (diseases and conditions of the heart and blood vessels).
• Endocrinology (diseases of the endocrine glands, which regulate hormones).
• Gastroenterology (diseases of the digestive system).
• Geriatric medicine (conditions and diseases in older adults).
• Hematology (diseases of the blood and blood system).
• Infectious disease (complex infections).
• Nephrology (diseases of the kidney and urinary system).
• Oncology (cancer).
• Pulmonology (lung diseases such as asthma, emphysema, and pneumonia).
• Rheumatology (immune system diseases and diseases of the joints).
• Sports medicine (the treatment of injuries to the bones, muscles, joints, tendons, or ligaments that result from physical activity).

Internists can be board-certified by the American Board of Internal Medicine, which is recognized by the American Board of Medical Specialties.