Hematology is considered part of internal medicine, pathology, physiology, and pediatrics.  Hematology is going to study the blood, blood forming organs, and blood diseases.   A person who suffers from coagulation issues will have to be seen by a doctor in the Hematology department. 

For example a hemophiliac is unable to stop bleeding when a blood vessel is broken.  The blood will not coagulate because the person is missing a clotting factor VIII or factor IX, depending on whether they have hemophilia A or B.  Hematology studies why the factor is missing and what can be used to treat the disease. Hematology has so far found that the disease is related to genetics, meaning it is hereditary.  The sufferer must get medical attention immediately if they suffer from hemophilia.