What Is Hematology?
Many people first hear the word “hematology” when they find out they have a cancer of the blood such as leukemia or lymphoma, or another blood problem. Learning what it is and what to expect can help you feel more confident and ready to take care of your health.
What does hematology mean?
Hematology is the study of blood and problems that affect the blood. The word comes from the Greek word haima, meaning blood. It focuses on how blood is made and how it works in the body. This includes red and white blood cells, platelets, bone marrow, lymph nodes, and the proteins that help your blood clot or stop bleeding.
There are two main parts of hematology:
- Benign hematology focuses on non-cancerous blood problems, like anemia, bleeding too much, or problems with blood clotting.
- Malignant hematology focuses on blood cancers, like leukemia, lymphoma, or multiple myeloma.
Which doctors treat blood problems?
A hematologist is a physician (medical doctor) who finds and treats problems with the blood. Some hematologists focus only on non-cancerous (benign) blood problems. Others treat only blood cancers (malignant). But most treat both types.
A hematologist oncologist is a doctor trained in both blood diseases and cancer care. Hematology oncology (hem-onc) is a type of oncology. Cancers that start in blood cells are different from cancers that form tumors in body organs or tissues and require different treatment approaches.
Sometimes a primary care or internal medicine doctor will treat common blood problems, like iron deficiency anemia. But if the problem is more serious or doesn’t go away - especially if it involves bleeding or clotting – they will refer you to a hematologist.
What does a hematologist do?
A hematologist may:
- Diagnose blood conditions using lab tests and exams
- Recommend and manage treatment
- Watch your condition over time
- Work with your other doctors to make sure you get the right care
Hematologists may work in hospitals, clinics, doctor’s offices, or labs. Some work in special programs for bone marrow or stem cell transplant or advanced treatments like CAR-T therapy.
What kinds of problems do hematologists treat?
Hematologist oncologists and other hematologists who treat blood cancers may care for people with:
- Leukemia
- Lymphoma
- Multiple myeloma
- Myelodysplastic syndromes
- Polycythemia vera and other myeloproliferative disorders
Hematologists also care for people with many different blood problems, including:
- Anemia (low red blood cells)
- Clotting problems like deep vein thrombosis (DVT) or hemophilia (a rare, inherited condition)
- Bleeding disorders like von Willebrand disease (a condition caused by lack of protein that helps blood clot)
- Too many or too few white blood cells or platelets
- Other inherited blood conditions like sickle cell disease or thalassemia
How are blood cancers and other blood problems diagnosed?
To learn more about your blood problem, a hematologist may order:
- Complete blood count (CBC) to check white and red blood cells, as well as platelets
- Blood chemistry tests, such as complete metabolic profile (CMP) to check how your liver and kidneys are working
- Bone marrow biopsy and aspiration to look at how your bone marrow makes blood
- Clotting tests to check how well your blood clots
- Genetic tests to check for any inherited conditions
These tests help the doctor understand what’s causing your symptoms and decide the best treatment for you.
What if I'm diagnosed with a blood cancer?
If you're diagnosed with a blood cancer, your hematologist (or hematologist oncologist) will guide you through the next steps. They’ll explain your specific type of cancer and treatment options. You may also meet with other doctors, nurses, and health care professionals, depending on your needs. Your cancer care team is there to support you every step of the way.
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
American College of Physicians. Hematology. Accessed at https://www.acponline.org/about-acp/about-internal-medicine/subspecialties-of-internal-medicine/hematology on July 24, 2025.
American Society of Clinical Oncology (ASCO). The oncology team. Accessed at cancer.net. Content is no longer available.
American Society of Clinical Oncology (ASCO). Types of oncologists. Accessed at cancer.net. Content is no longer available.
National Cancer Institute (NCI). What is hematologic cancer? Accessed at https://www.cancer.gov/publications/dictionaries/cancer-terms/def/hematologic cancer on July 24, 2025.
National Cancer Institute (NCI). What is hematologist? Accessed at https://www.cancer.gov/publications/dictionaries/cancer-terms/def/hematolgist on July 24, 2025.
Last Revised: August 8, 2025
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