What Is Hematology?

Hematology is the medical specialty having to do with the study and treatment of diseases of the blood and the organs that make blood cells; the word derives from the Greek “haima,” which has come over into American English as the root “hema.” Hematologists who practice clinical medicine (some hematologists prefer to stick with laboratory research) diagnose and treat persons who have diseases of the various types of blood cells—the leukocytes or white cells, the red cells, and the platelets— and the bone marrow and lymphatic system, as well as problems with the clotting system and conditions involving the need for transfusion of various kinds. Hematology covers the range of benign and malignant (cancerous) blood diseases such as leukemia and lymphoma, which is why the field is closely related to the practice of oncology. Many, but not all, oncologists do additional training to become board-certified in hematology as well, and the two disciplines are typically studied simultaneously in training programs.

Hematology is one of the specialties that retains a tight relationship with laboratory medicine, from diagnostic testing to transfusion medicine to pathology. It is an unusual day in which I don’t make at least one trip to the hospital laboratory to check on something in person.

Not every condition involving the blood comes under the care of a hematologist. For instance, even though high sugar or glucose levels appear in the blood in diabetes mellitus, you would not normally go to a hematologist to have your diabetes taken care of. Similarly, a high or low potassium level in the blood is managed by a primary care health provider or perhaps a nephrologist (specialist in kidney diseases).