Internal medicine is one of the most popular specialties physicians choose. Internists diagnose and provide comprehensive medical treatment for adults with a wide variety of conditions. After graduating from medical school, a three-year residency in internal medicine is required to become board certified. Many internists don’t stop there.

Some internal medicine physicians choose to pursue a subspecialty. Doctors who decide to work in a subspecialty are required to receive additional training in the management of diseases affecting a specific organ system or a certain type of disease. There are 13 subspecialties in internal medicine, which require completion of additional training in the form of a fellowship. Below are 5 examples of common subspecialties.

Cardiology: Internal medicine doctors who choose to specialize in cardiology treat patients with cardiovascular conditions, such as coronary artery disease, congestive heart failure, and hypertension. After completing an internal medicine residency, a two to three-year cardiology fellowship is required. A general cardiology fellowship prepares doctors in non-invasive cardiology, which involves doing diagnostic catheterizations, stress tests, and echocardiograms. After completing a cardiology residency, physicians may sit for the exam to become board certified.

For those who wish to specialize further, they may want to consider an additional fellowship in interventional cardiology, which involves performing invasive procedures, such as stenting and angioplasty.

Infectious Disease: An infectious disease doctor is an internal medicine specialist who receives additional training in order to diagnose and treat various types of infectious disease. Doctors who choose this specialty are experts in treating diseases caused by viruses, bacteria, parasites and fungi. Infectious diseases can be complicated and affect any organ including the brain, heart, lungs and bones.

Infectious disease doctors also have specialized training in epidemiology and immunology. In order to become board certified as an infectious disease specialist, a two to three-year fellowship in infectious disease is required.

Pulmonology: Pulmonologists have specialized training to treat people with problems associated with lung disease. Some typical conditions a pulmonary doctor may treat include cystic fibrosis, pulmonary hypertension, chronic obstructive pulmonary disease and asthma. In addition, pulmonologists may consult on cases where patients have an infectious disease, such as pneumonia or tuberculosis. If you follow this career path, typical tasks may include interpreting diagnostic tests, such as pulmonary function tests and performing procedures including bronchoscopies and endotracheal intubations. The road to becoming a pulmonologist starts similar to other internal medicine subspecialties. After residency is completed, a two or three-year fellowship in pulmonary medicine is required. A three-year fellowship combines critical care and pulmonary.

Oncology: Another subspecialty of internal medicine involves the treatment of cancer. Medical oncologists diagnose and treat people with various types of neoplasms including lung, breast and colon cancer. They oversee a patient’s general care and refer patients to specialists, such as radiation and surgical oncologists. Medical oncologists may also perform procedures, such as bone marrow biopsies and prescribe a treatment protocol, which may involve chemotherapy and immunotherapy.

Oncologists also play a role in cancer prevention. They may identify individuals at a high risk of developing cancer and recommend ways to reduce their risk. In addition to an internal medicine residency, medical oncologists must complete a two-year fellowship in oncology. Three-year residencies are also an option for those who want a combined specialty in hematology and oncology.

Endocrinology: An endocrinologist generally treats conditions that involve glands, such as the thyroid and adrenal gland. They may diagnose and treat patients with a variety of conditions including pituitary disorders, diabetes, obesity and metabolic conditions. Endocrinologists may also treat hormonal problems and growth disorders. In order to be eligible to become board certified, doctors need to complete a two to three-year fellowship. A three-year fellowship in endocrinology usually combines clinical work with research.

That’s just a small sample of the exciting specialization options which are available to internal medicine physicians. We’ll follow up soon with another post about where these different types of physicians work. In the meantime, this job board has a lot of positions available and can give you a pretty good idea of the available job types.