Haematology is the study of blood and its components. The haematologist specialises in how and why and where these components are manufactured in the body and what their normal functions are. He also knows what processes are involved in the clotting of blood.
The haematologist is trained to diagnose and treat disorders of the blood by running the appropriate laboratory tests. Amongst other things he knows how to prevent blood clots from forming by, for example, prescribing medicines that thin the patient's blood.
Transfusions and congenital disorders of the blood, such as haemophilia, also come under his area of expertise. To treat haemophilia he can arrange for, and supervise, substitution therapy. This method of treatment involves regularly injecting the patient with the factors that are missing from his blood.
The haematologist is of importance when it comes to the diagnosis and treatment of leukaemia (cancer of the blood). He often works with the oncologist or is himself trained in oncology.