What’s the Difference Between a Hematologist and an Oncologist?

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It can be somewhat confusing to distinguish between a hematologist and an oncologist since they both deal with blood and its disorders. We will try to simplify this for you. What’s the difference between a hematologist and an oncologist?

What Do Each Treat?


Hematology is a subspecialty of internal medicine. A hematologist is a healthcare provider whose specialty is diseases that affect your blood, bone marrow, and lymphatic system. They diagnose, treat, and manage diseases that affect your blood cells. Blood diseases can be benign (non-cancerous) or malignant (cancerous). 

Some diseases are concerned with blood flow or lack thereof (clots) while others diseases make you bleed more. Blood diseases or blood cancers can have mild symptoms or be life-threatening. 

Blood disorders treated by hematologists include some of the following:

  • Anemia, or not enough red blood cells to carry oxygen like iron deficiency anemia
  • Hemophilia, an inherited blood disease that impairs clotting
  • Sickle Cell Anemia, an inherited disease that affects the shape of red blood cells
  • Von Willebrand Disease, the most common bleeding disorder in the US
  • Obstructive disorders like deep vein thrombosis (DVT)
  • Systemic blood disorders like sepsis or septic shock

Hematologists also treat blood cancers like leukemia, lymphoma, and myeloma.


A hematologist must complete a 4 year medical school, 3 years residency, and 3 to 5 years of fellowship training.


An oncologist diagnoses and treats all kinds of cancer. There is a natural overlap between oncology and hematology because many types of cancers begin in the blood cells in bone marrow and the lymphatic system.

An oncologist is usually the main healthcare provider for a patient with cancer. They design treatment plans, offer supportive care, and sometimes coordinate treatment with other specialists.

In addition oncologists:

  • Confirm or rule out if and where cancer is present
  • Provide an accurate cancer diagnosis and the stage
  • Provide treatment plans and recommendations
  • Oversee the course of the treatments
  • Offer an early prognosis and a prediction of your recovery timeline

Oncologists may focus on certain specialties, for example, a gynecologic oncologist treats ovarian, uterine, and cervical cancers. A hematologist-oncologist focuses on blood cancers, and a pediatric oncologist specializes in cancers in children and teens.


An oncologist begins with 4 years of medical school, followed by 2 to 5 years residency program, then obtaining a medical license and becoming board certified, and may complete a graduate or fellowship training in a specialty.  

If you remain unsure about the difference between an oncologist and a hematologist, talk with your care team so you know what to expect throughout your care moving forward.

Contact New Jersey Cancer Care if you have been referred to our practice and are concerned about upcoming cancer care.