What Are The Sub-Specialties Of Internal Medicine?

Internal medicine is the medical specialty that deals with diagnosing, treating and preventing an extensive range of diseases or illnesses affecting the internal organs or body parts of adults and adolescents. Those physicians who specialize in internal medicine are referred to as internists, internal medicine physicians or internal medicine doctors.

Internal medicine doctors have the option to further specialize in internal medicine by getting additional training in the sub-specialty of internal medicine. In today’s article, we highlight the various sub-specialties of internal medicine and the specific diseases or illnesses that the internists have to deal with.


Sub-specialties of internal medicine acknowledged by the American Board of Internal Medicine:

Here is the list of internal medicine sub-specialties accepted by the American Board of Internal Medicine:

  • Adolescent medicine
  • Allergy, Asthma, and Immunology
  • Critical care medicine
  • Cardiology
  • Clinical cardiac electrophysiology
  • Interventional Cardiology
  • Endocrinology
  • Gastroenterology
  • Transplant Hepatology
  • Geriatric medicine
  • Hospital medicine
  • Hematology
  • Infectious diseases
  • Oncology
  • Nephrology
  • Pulmonology
  • Rheumatology
  • Sleep medicine
  • Sports medicine

Here’s the detailed overview of each sub-specialty:


Adolescent medicine:

Adolescent medicine experts emphasize on the physical, psychological, social and sexual growth of adolescents and young adults.

Various diseases or health issues that commonly occur during adolescence are treated and managed by the internal medicine doctors. These include:

  • Sexually transmitted diseases (STDs)
  • Sexual activity (such as sexual abuse, masturbation)
  • Unintended pregnancy
  • Birth control
  • Menstruation/Menstrual disorders (such as dysfunctional uterine bleeding, amenorrhea, and dysmenorrhea)
  • Substance abuse or drug abuse
  • Acne related problems
  • Eating disorders (such as anorexia nervosa, bulimia nervosa)
  • Mental illnesses (such as personality disorders, depression, and suicide, anxiety disorders, bipolar disorder, and schizophrenia)
  • Delayed puberty


adolescent medicine


Allergy, Asthma, and Immunology:

It involves diagnosing, treating and managing the allergies, asthma, and disorders that are related to the immune system.

The diseases or illnesses that are seen by the allergist or immunologist include:

  • Allergic diseases of an eye (such as allergic conjunctivitis)
  • Respiratory-tract related disorders (such as asthma, sinusitis, allergic rhinitis, occupational lung diseases, and hypersensitivity pneumonitis)
  • Allergic conditions related to the skin (such as contact dermatitis, atopic dermatitis, and urticaria)
  • Adverse reactions to foods, vaccines, drugs, stinging insects and other agents
  • Gastrointestinal disorders that are caused by the immune responses to the foods (such as eosinophilic esophagitis)
  • Diseases that primarily affect the immune system (it includes primary immune deficiencies, for instance, severe combined immune deficiency syndromes, complement deficiency, antibody deficiencies, phagocytic cell abnormalities and acquired immune deficiency)
  • Diseases that are linked to autoimmune responses to the self-antigens (such as auto-inflammatory syndromes)
  • Systemic diseases (such as anaphylaxis)

allergy, asthma, and immunology


Critical care medicine:

Critical care medicine or intensive care medicine is the branch of medicine that deals with diagnosing and managing those life-threatening conditions that may need advanced life support and intensive care and monitoring.

The life-threatening conditions that are seen by the intensivist include:

  • Cardiovascular instability (such as hypertension or hypotension)
  • Cardiac arrhythmias
  • Airway or respiratory failure
  • Acute renal failure
  • Multiple organ failure


critical care medicine



This sub-specialty deals with the diagnosis, treatment, management, and prevention of cardiovascular diseases (those related to the heart and blood vessels).

The diseases that are normally seen by the cardiologist include:

  • Coronary artery disease
  • Congenital heart defects
  • Heart failure
  • Arrhythmias
  • Acute myocardial infarction
  • Valvular heart disease
  • Disorders of the arteries, veins and pulmonary circulation
  • Electrophysiology




Clinical cardiac electrophysiology:

This branch of cardiology is also called cardiac electrophysiology, electrophysiology or arrhythmia services and deals with the study and treatment of the rhythm disorders of the heart. Those cardiologists who have expertise in this branch of medicine are called electrophysiologists.

Electrophysiologists are trained in the technique, performance, and function of the electrical activities of the heart. They assist and guide the other cardiologists and cardiac surgeons for managing the heart rhythm disturbances (called arrhythmias). They are also trained in performing interventional and surgical procedures while treating cardiac arrhythmia.

clinical cardiac electrophysiology


Interventional Cardiology:

It is the branch of cardiology that deals with the treatment of structural heart diseases by using specifically the catheter-based approach.

The procedures that are performed by the interventional cardiologists include:

  • Angioplasty (to treat obstructed arteries or veins)
  • Percutaneous coronary intervention or coronary angioplasty (to treat coronary artery disease)
  • Coronary thrombectomy
  • Stent placement
  • Valvuloplasty (to treat narrowed cardiac valves)
  • Percutaneous valve replacement
  • Percutaneous valve repair
  • Congenital heart defects correction (to repair atrial and ventricular septal defects, great vessel’s angioplasty and closure of the patent ductus arteriosus)

interventional cardiology



This sub-specialty deals with the diagnosis and management of the disorders of the endocrine system and its specific secretions that are called hormones.

The typical conditions that are seen by the endocrinologists include:

  • Pituitary diseases (such as tumors, over-production or under-production of the pituitary hormones)
  • Hypothalamic disorders (abnormal water and sodium balance)
  • Thyroid diseases (such as hypothyroidism, hyperthyroidism, goiter, or nodules)
  • Parathyroid abnormalities (such as hypercalcemia or hypocalcemia)
  • Pancreatic endocrine disease (such as diabetes mellitus)
  • Bone metabolism (such as osteoporosis)
  • Lipid metabolism
  • Adrenal cortex dysfunction (such as glucocorticoid, mineralocorticoid, sex hormone abnormalities)
  • Gonadal disease (such as reproductive disorders and hypogonadism)




This sub-specialty focuses on the diagnosis, treatment, and prevention of the disorders of the entire gastrointestinal tract that includes the organs: esophagus, stomach, small intestine, liver, pancreas, gall bladder, large intestine (colon), and rectum. Internists that sub-specialize in this field are called gastroenterologists.

Significant diseases that are seen by the gastroenterologists include:

  • Gastrointestinal Cancers
  • Gastrointestinal bleeding
  • Liver cirrhosis
  • Gallstones
  • Gastroenteritis
  • Inflammatory bowel disease

Significant diagnostic procedures performed by the gastroenterologists include:

  • Endoscopy
  • Colonoscopy
  • Liver biopsy
  • Endoscopic ultrasound
  • Stool test
  • Barium swallows
  • ERCP (endoscopic retrograde cholangiopancreatography)




Transplant Hepatology:

It is the sub-specialty of gastroenterology that deals with the management of the advanced disease of the liver.

Through training, the experts – called “transplant hepatologists” – comprehensively understand the hepatopathology and diagnostic methods to manage and evaluate the potential patients of a liver transplant. These experts also manage the patients of liver transplant both before and after the transplantation procedure.

transplant hepatology

Geriatric medicine:

Geriatric medicine or geriatrics is the sub-specialty of internal medicine that focuses on the health care and well-being of older adults. A physician who specializes in geriatrics is called geriatrician. The main aim of this field is to promote the health of elderly people by treating, managing and preventing the diseases and disabilities in them.

The significant diseases/disorders that are seen by the geriatrician include:

  • Heart disease
  • High blood pressure
  • High cholesterol level
  • Arthritis
  • Osteoarthritis
  • Osteoporosis
  • Rheumatoid arthritis
  • Dementia
  • Parkinson’s disease
  • Atherosclerosis
  • Palliative care

geriatric medicine


Hospital medicine:

This medical specialty exists in some countries (America, Australia, and Canada) as the sub-specialty of internal medicine. It deals with the care of those hospitalized patients who are acutely ill.

Those internists who primarily provide comprehensive care to the hospitalized patients (only during their stay at the hospital) are referred to as hospitalists.

hospital medicine



This internal medicine sub-specialty deals with the study of those diseases that are related to blood. It is concerned with managing, treating, preventing the diseases that affect the blood and its components such as blood cells, platelets, blood proteins, hemoglobin, bone marrow, blood vessels, spleen and the process of coagulation. Such significant diseases that are seen by the hematologists include:

  • Anemia
  • Blood clots
  • Hemophilia
  • Blood cancers (such as multiple myeloma, leukemia, and lymphoma)
  • Other bleeding disorders



Infectious diseases:

This sub-specialty – also called infectiology – deals with diagnosing, treating and controlling the infections caused by bacteria, virus, or parasite. The internists who practice infectious disease medicine are called infectious disease specialist or infectiologist.

Typically, most common infections are treated by general internists or other physicians but infectious disease specialists are called upon to diagnose unknown infections and to manage unusual, difficult, or complicated infections.

infectious diseases



It is the internal medicine sub-specialty that deals with the diagnosis, treatment, and prevention of cancer. Internists who practice oncology are called “oncologists”.

The treatment methods of cancer that an oncologist deals with are chemotherapeutic (involves treatment through anti-cancer drugs/chemicals) and/or immunotherapeutic (involves treatment through artificially stimulating the immune system).



This internal medicine sub-specialty deals with the diagnosis and treatment of kidney diseases.

It also involves the study of normal function of the kidney, preservation of the kidney health and the treatment of kidney diseases through diet, medication, and renal replacement therapy – it includes dialysis and kidney transplantation. This branch of internal medicine also studies the systemic conditions affecting the kidneys (such as autoimmune disease and diabetes) and the systemic diseases occurring as a consequence of the kidney dysfunction (such as hypertension and renal osteodystrophy).

A physician who practices nephrology is called a “nephrologist”.





It deals with the diagnosis, treatment, and management of the diseases of the respiratory system that includes lungs, thoracic cavity, upper airways, and chest wall.

Disorders that are commonly treated by the pulmonologists include:

  • Asthma
  • Pneumonia
  • Chronic obstructed lung disease
  • Emphysema
  • Lung cancer
  • Occupational lung disease
  • Complicated lung infections (such as tuberculosis, cystic fibrosis, and pulmonary hypertension)





It focuses on diagnosing and treating the disorders of the muscles, joints and connective tissues. Although rheumatologists primarily deal with joint diseases, they also have expertise in managing a wide array of disorders related to the musculoskeletal system, including the systemic inflammatory and autoimmune diseases.

Conditions that are commonly treated and evaluated by the rheumatologists include:

  • Rheumatoid arthritis
  • Osteoarthritis
  • Osteoporosis
  • Systemic lupus erythematosus
  • Psoriatic arthritis
  • Crystalline diseases (such as gout)
  • Inflammatory muscle diseases (such as dermatomyositis and polymyositis)
  • Fibromyalgia
  • Common musculoskeletal and sports injuries



Sleep medicine:

This sub-specialty focuses on diagnosing and treating the disturbances and disorders related to sleep. The most common sleep disorders include sleep apnea and insomnia.


sleep medicine

Sports medicine:

This internal medicine sub-specialty deals with the treatment and prevention of the injuries that are related to sports (especially athletics) and exercise and focuses on physical fitness.

Significant disorders that are seen by sports medicine specialists include:

  • Sports injuries
  • Muscle strain
  • Trauma

sleep medicine



Island Medical Consultants is an internal medicine center located in Staten Island, NY and provides high-quality comprehensive internal medicine care to the people of all age groups. To consult our internal medicine doctors, you can request an online appointment or call us at 718.727.1898 for any medical emergency.