The hematologist is the doctor who specializes in blood diseases. It is responsible for diagnosing and treating blood disorders such as anemia, leukemia, lymphoma, hemophilia, and thrombosis. It uses laboratory tests and other diagnostic methods to evaluate the composition and function of the blood, as well as the health of the bone marrow and lymph nodes. It is advisable to see a hematologist if symptoms such as unexplained fatigue, abnormal bleeding, frequent bruising, recurrent infections or abnormal blood test results occur.